Anis Chaari
email: anis.chaari@ibisc.fr

Mohamed Ben Ahmed
email: mohamed.benahmed@riadi.rnu.tn

Sylvie Lelandais
email: s.lelandais@iut.univ-evry.fr

A Combining approach

Keywords: Biometry, face identification, clustering, learning, biometric databases, results fusion. I

de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

In his daily environment, a person needs to be identified in a multitude of contexts: to enter his building, to reach its place of work, to withdraw money in a distributor, to pay in a store, to reach its data-processing station of work... A wide variety of applications which require reliable recognition schemes to confirm or to establish the identity of an individual. In order to improve identification techniques, research has known for a few years a spectacular revival and a major interest with the biometric data, i.e. with the specific characteristics to each person: her voice, fingerprints, face pattern, hand geometry, signature and even DNA [1]. Thus, techniques based on biometrics enjoy a general passion favoured by an increased request of security.

According to the specifications of a given application, biometric recognition techniques are applied within the framework of authentication or identification process what implies two different modes of research and consultation of the databases. The biometric identification process consists in matching features of the unknown identity with the equivalent templates of all users, already stored in a knowledge base. The unknown person to be recognised or the probe (image containing his face by example) is identified like the user having the template which resembles the more, according to a given criterion, with the query features (1:N match). We note that the system can act in a closed or an opened universe [START_REF] Li | Handbook of Face Recognition[END_REF]. In the closed universe, every probe is in the database. Whereas, in an opened universe, unknown people (recorded or not in the knowledge base) could be introduced to the system. Few systems are proposed in the literature treating recognition in opened universe. They proceed with the rejection, in a first step, of faces (subjects) not recorded in the database and keep only the known faces to operate, in a second phase, identification in a closed universe. On the other hand, authentication consists in matching the extracted query features with only those of the proclaimed identity (1:1 match). Here, it is a question of classifying the user like a genuine (true user) or an impostor. Intensive research during these twenty last years pushed this authentication technique which constitutes the base of access control systems to acceptable performances and maturity. However, within the framework of the more general identification, we don't have any priori information concerning the identity of the face. Thus, identification systems have a significant decrease of performances according essentially to the potential number of users of the system (size of the database) under real conditions of application.

To evaluate identification systems we usually seek how good an algorithm is at identifying a probe image (i.e. if the top match is correct). But, in the event of error, it is useful to know if the correct answer is in the top n matches. Then we trace the cumulative match scores which represents the probability that the desired result is among the top n matches [START_REF] Phillips | The FERET evaluation methodology for face-recognition algorithms[END_REF].

The deployment of biometric solutions in the airports and at countries borders implies gigantic databases at a national scale. In spite of the fast proliferation of these large scale databases, the community of research up to now is concentrated only on the performances in small databases while neglecting questions of scalability and execution speed which are significant for large scale applications. In such applications, the response time and the effectiveness of research become also significant in addition to the precision. Traditional databases classify recorders in an alphabetical or numerical order for an effective research. However, in image databases and especially facial ones, there is no natural order by which we can classify that biometric data. Classification and indexing in these databases constitute the principle challenges to raise [START_REF] Palla | Classification and Indexing in Large Biometric Databases[END_REF].

1

In this paper, we develop face images and especially appearance-based Eigenfaces method to generate holistic and discriminant features and template. These features vectors, which describe faces, are often used to establish the required identity in a recognition process. In this work, we introduce a clustering process which aims to split biometric databases into partitions and to simplify consequently recognition task within these databases. Various studies were undertaken to adjust feature extraction. Several test series are carried out to asses the robustness and the effectiveness of our proposed approach. To finish, we propose to combine and to fuse clustering classifiers and identification processes.

II. EXPERIMENTAL METHODS

A. Principal Component Analysis

Principal component analysis (PCA) [START_REF] Jolliffe | Principal Component Analysis[END_REF] is a dimensionality reduction technique based on extracting the desired number of eigenvectors with the highest variance of the multidimensional data. PCA is closely related to the Karhunen-Loève Transform (KLT) [START_REF] Kirby | Application of the karhunen-loeve procedure for the characterization of human faces[END_REF] which generates an orthogonal basis and decorrelate perfectly data vectors. Kirby and Sirovich [START_REF] Kirby | Application of the karhunen-loeve procedure for the characterization of human faces[END_REF] proposed in 1990 the use of PCA for face analysis and representation. Their paper was followed by the Eigenfaces technique by Turk and Pentlnd [START_REF] Turk | Eigenfaces for recognition[END_REF], the first application of PCA to face recognition. Since, several face recognition systems presented in the literature use this appearance-based method [START_REF] Yang | Two-dimensional PCA: a new approach to appearance-based face representation and recognition[END_REF][START_REF] Wang | Subspace evolution analysis for face representation and recognition[END_REF].

A two dimensional image of size p by q pixels is generally represented as a vector of size n ( n = p x q ) in high dimensional space. Facial images represented as vectors of samples x can be expressed as linear combinations of the lower dimension orthogonal basis Ф i :

∑ ∑ = = ≈ = Φ m i i i n i i i i a a x 1 1 : φ φ (1)
The orthogonal basis Ф defines the face space at a lower dimension m (m << n) by resolving the problem

ΦΛ = Φ C (2)
where C is the covariance matrix for input x:

∑ - - = T x x x x C ) ).( ( . ( 3
) T m ] ,..., [ 1 φ φ = Φ
is the eigenvectors matrix of C, and Λ is the associated eigenvalues. Eigenvectors which have the same dimension as the input face images are called eigenfaces. Fig. 1 shows an example of few top eigenfaces.

B. Identification Process

All images of known faces are projected onto the built face space Ф to find sets of weights that describe the contribution of each image vector. Thus, each face in the Enrolment database is represented by a feature vector of weights obtained by projecting its correspondent image on the face space Ф. If we have several facial images per one identity in the database, we can compute as well one feature vector per image as one template vector per identity. In the first case, a person identity is described by several feature vectors. Whereas in the second case, only one kernel feature vector characterize the person identity. When an unknown image of test is given to identify, that image is projected onto the face space to obtain its set of weights. The identification of the test image is performed by finding the known image in the database to which the weights are closest to the weights of the query image within the meaning of a similarity measurement.

III. CLUSTERING APPROACH

We assume the existence of global facial characteristics which allow to subdivide population into a well separated groups. Research community focuses supervised methods to classify facial images by gender or ethnicity [START_REF]Invariant gender identification[END_REF][START_REF] Costen | Sparse models for gender classification[END_REF]. They used facial features which could be incompatible with the learned distributions. Unlike these approaches, we address, in this work, unsupervised classification methods to discriminate facial biometric data.

We propose to reduce the search space by partitioning the database into several clusters (so called bins) using the K-Means clustering algorithm. Our biometric feature vectors described above are assimilated to multi-dimensional data points occupying the multi-dimensional face space Ф. Data clustering algorithms have the aim of identifying the sparse and the crowded places of this space and divide consequently the distribution points into groups in such way to minimize the intra class variance and maximize the inter class variance. Clustering problem is then formalised as follows: given the desired number of clusters K and a dataset of N points, and a distance-based measurement function, it is a question of finding a partition of the dataset that minimizes the value of the measurement function [START_REF] Jain | Data Clustering: A Review[END_REF]. Data points are then assigned to clusters C i so that each cluster must contain at least one data point; and each data point may belong to one and only one cluster as show the below formulation:

j i Ø, C C and j i 1 ≠ ∀ = ∩ Φ = = ∪ K i i C (4)
Following such binning, the biometric database will be partitioned such that features or templates in each bin are similar and correspond to a statistical class. Given a facial image to establish the identity of a person, its feature vector is firstly computed and then compared to each class center (so called centroid). In fact, each bin is represented by its centroid. Query identity is potentially found in the closest bin. However, by increasing the number of bins, probability to find the query identity in the closest bin decreases. Thus, to prevent missing the bin in which lies the query identity, we performed, in a previous work [START_REF] Chaari | Face classification scheme simplifying identification in large scale biometric databases[END_REF], research in the P closest bins. The parameter P is related to the number K of bins and the intrinsic quality of features and related clustering method. The value of P is experimentally determined to assure that any bin containing the search identity is missing.

Unlike this last study, we operate clustering into few bins. Thus, P parameter is easier to estimate. If we perform clustering into three bins, for example, we can retain a subset made of the closest bin (P = 1) or a subset resulting from the two closest bins (P = 2). Then, we study whether the required identity is in the kept subset. We denote by C-Identification, the step where we look for the nearest bin(s) to the query image. Then, identification process is performed only on the identities belonging to these bins. Unlike Identification process which compares query identity with identities from the whole database, we denote by Sub-Identification the process of identification performed only on identities from the kept database partition.

A very significant point in an indexing problem is to extract pertinent features which constitute the input of the classification process. We distinguish through our experiments the main pertinent features as well for identification task as for clustering task. We assess three adaptive spaces dimensionalities by defining an adaptive number of eigenfaces from the face space Ф.

Thus, we propose to perform clustering followed by identification process. Clustering process aims to split the biometric database into disjoint partitions and to keep a subset from the initial database where the query identity is most probably belonging. This allows to simplify consequently identification task within these databases.

IV. DATA SET The XM2VTS database is a multimodal database consisting of 2D and 3D facial images, video sequences and speech recordings. Our experiments were performed on the 2D face images from the XM2VTS database [START_REF] Messer | XM2VTSBD: The Extended M2VTS database[END_REF]. This extended database contains 4 recording sessions of 295 subjects taken over a period of 4 months. Since the data acquisition was distributed over a long period of time, significant variability of appearance of clients, e.g. changes of hair style, facial hair, shape and presence or absence of glasses, is present in the recordings (cf. fig. 2). Two shots per session was recorded what make a total number of eight image per subject. The database is primarily intended for the task of person verification, where an individual asserts his identity. Lausanne protocol [START_REF] Luettin | Validation Protocol for the extended M2VTS database (XM2VTSDB)[END_REF] was defined on XM2VTS database especially for authentication assessment. The protocol was designed for an open test scenario where persons, unknown to the system, might claim access. The database was randomly divided into 200 clients, 25 evaluation impostors, and 70 test impostors. On the other hand, client set was divided into three sets: training set, evaluation set, and test set. Two different evaluation configurations were defined. We extend the first configuration to assess our identification system. Then we conceive three other configurations that we detail in the next section.

V. EXPERIMENTAL STRATEGIES We followed Lausanne protocol to assess our system performances: we use the established client set of 200 persons and we operate in a closed universe. Each person has 8 frontal images: 4 different sessions with 2 images per each session. Then, we divide this set into different subset: the training, the enrolment and the test sets. The training set is used to build the face space. The enrolment set is selected to produce feature vectors and templates of subjects in the database. The test set is selected to simulate our identification tests.

We conceive four different such subdivisions, that we denote experts, in order to show the importance of the learning task (cf. Table 1). Experts differ by the distribution of training and enrolment sets. Thus, each expert will learn differently to extract features and characteristics representing facial images.

We give here the first expert details. Three images of the first shots of the first three sessions were used for training purpose (cf. Table 2). The other three images of the same sessions were used to enrol the identity in the knowledge database. The last two image of the fourth session were used for the classification and identification tests. Thus, we have a set of 600 training images, a set of 600 enrolment images and a set of 400 images for tests. The first and the third experts are based on a training set from facial images of the first three sessions whereas expert two and four learn from a selected set from the four sessions. One can affirm that these two last experts (2 and 4) have certainly a more significant detail level of an individual facial image from the database than the two other experts (1 and 3). Indeed, facial images of the all four sessions enrich the knowledge of these experts 2 and 4. However, we see through experiments and through following results that the size of the training set has a greater effect than the richness of the training set with more multi-session facial images.

VI. RESULTS

A. Pertinent feature vector

To evaluate identification systems we usually seek how good an algorithm is at identifying a probe image (i.e. if the top match is correct). But, in the event of error, it is useful to know if the correct answer is in the top n matches. Then we trace the cumulative match scores (cf Fig. 3) which represents the probability that the desired result is among the top n matches [START_REF] Phillips | The FERET evaluation methodology for face-recognition algorithms[END_REF].

We illustrate mainly, in this part, identification rate and the top matches rank i.e. the response number from which we have 100% of identification rate (cf Fig. 3). These two measures allow us to choice pertinent features for both identification and clustering processes.

First, PCA is performed on the original training database. We keep eigenfaces (principal components) which define a percentage of the total inertia. Indeed, we compute the inertia of each eigenfaces relatively to its eigenvalue as below:

∑ = n i i j 1 λ λ (5)
where λ j is the eigenvalue associated to the j th eigenfaces.

The total inertia of the j th first eigenfaces is defined by [START_REF] Kirby | Application of the karhunen-loeve procedure for the characterization of human faces[END_REF]:

∑ ∑ = = n i i j i i 1 1 λ λ ( 6
)
We assess different face space sizes and keep first eigenfaces which define 80%, 85% and 90% of the total inertia. For the expert 1, for example, these inertia rates are obtained with 44, 66 and 105 eigenvectors respectively what correspond to feature sizes (see table 3). Table 3 shows, identification rate and the top matches rank performances of Eigenfaces recognition method for various feature vector sizes and for all experts. We seek feature vectors maximizing the identification rate and minimizing the top matches rank.

We obtain best recognition rate with feature vectors corresponding to 90% of the total inertia of the face space. A rather smallest feature vector size provides worst recognition rate. On the other hand, we remark that recognition rate increase significantly through the four experts due to the richness and the size of the training set. Indeed, we used training dataset of 600, 800, 1200 and 1600 images for the first, the second, the third and the fourth expert respectively. Furthermore, the use of facial images of four sessions for the second expert training, adds nothing compared to the first expert. In fact, expert one's performances are obtained with a training set of only three sessions recording images. One can argue, that XM2VTS database does not contain enough appearance changes through sessions since it was taken in well controlled conditions. However, while considering the top match rank of the system, we don't have a clear dynamic by the different experts. For example, smallest feature vectors provide a better top match rank performances for the third expert, while the reverse is true for the fourth expert. If we consider that we have as many clusters as subject or identity in the database, the top match rank define top clusters in which lie the query identity. We experiment in the following section the k-means clustering method to classify identities and to reduce the search space.

B. Clustering results

We performed clustering in two and three bins. We show in the below table statistics of the kept identities from the closest bin(s). For the clustering into two bins, we give the maximum and the minimum population of bins and the mean number of identities in the retained subset. For the three bins clustering, we show the same statistics by keeping either one bin (P=1) or the two closest bins (P=2) as a retained subset. Switch the kept database subset defined from closest cluster(s), answers are as below:

• "Right": the query image identity belongs to the kept database subset.

• "False": the query image identity doesn't belong to this subset.

Then, C-Identification rate is computed as the rapport between the number of right matches and the total query image number. We developed the same features defined above for Identification purpose. Table 5 presents the C-Identification rate, obtained by Eigenfaces feature vectors and K-means clustering algorithm.

We remark that feature vectors perform similarly for each expert. We opt, in this case, for smallest features which imply a reduced space dimensionality for the clustering problem. Thus, we extend experimentation to smaller features. We see clearly through the curves that C-Identification rate is almost the same for a given expert and for various feature vector sizes. The first rate value with 21% of total inertia correspond to a feature of one attribute. We show in the table 5, eigenfaces feature vector sizes of the first expert and for various inertia percentages. We propose, on the other hand, to combine in cascade clustering and identification. Table 6 shows all experts results for different feature sizes. Unlike C-Identification results, Sub-Identification performs better with more complete feature vectors resulting from 90% of the eigenfaces inertia. In addition, we have a consequent gain in computing time between Identification process (cf table 3) and both C-Identification and Sub-Identification processes (cf table 6). These results lead us to propose a new strategy. The first clustering step (C-Identification) will use Eigenfaces method with a short feature vector. Then, identification step will use rather a complete feature vectors with 90% of eigenfaces inertia.

We remark that the Sub-Identification rate doesn't exceed C-Identification rate. In fact, some identities are misclassified and false matched by the C-Identification process. We study, in the next section, noise effect on our result.

C. Noise effect

To evaluate the robustness and the performance of our approach against noise effect, we performed another test series feature vectors with 105 attributes. We took the most trained fourth expert which make the most powerful decision. We disturbed facial images with random grey level noisy pixels. Table 7 shows results of Identification, C-Identification and Sub-Identification on query facial images disturbed at several levels of noise.

We remark that a sparse random noise up to 10% of the image don't affect Identification performance. However, we can go only to 1.6% of noise before degrade Clustering results. Beyond that, we register a decline in C-Identification rate and especially Sub-Identification rate which accumulate clustering and identification false matching results.

D. Fusion scheme

We propose finally, a parallel fusion scheme and a decision maker protocol determining the searched identity or simplifying the search database in the worst case. 5 summarizes fusing approach. We use simply the AND/OR fusion rules. In the case where Identification process give the same response that Sub-Identification one, we operate an AND rule and the system return an identity response. However, in the opposite case and if the identity returned by the Identification process doesn't exist in the kept subset, we proceed to do an OR fusion rule to keep a partition which contain potentially the searched identity. We developed this fusing scheme on the first expert. We obtain 78.5% of right identification (AND rule). In the other cases, we perform a new subset constituted from the elaborated subset issued from the clustering task and the identity returned by the Identification process. We miss only 9 query images from a set of 400 query faces. We have only 2.25% of false matching rate.

VII. CONCLUSION AND PERSPECTIVES

We have proposed in this paper a framework of clustering and partitioning face biometric databases. Clustering was achieved on Eigenfaces features using the k-means clustering algorithm. Our future work involves to implement and to combine with Eigenfaces other representation method and other modalities. In the other hand, we have to test other clustering methods and to look for optimal number of classes. We plan also to extend the evaluation of our recognition algorithms with a large scale database gathered from various face databases.

Figure 1 .

 1 Figure 1. Five top eigenfaces computed from XM2VTS client set.

Figure 2 .

 2 Figure 2. Sample of images from the XM2VTS database

Figure 3 .

 3 Figure 3. Cumulating match Scores (CMS) with a feature vector of 100 components -expert 1.

Figure 5 .

 5 Figure 5. Fusing scheme Fig.5summarizes fusing approach. We use simply the AND/OR fusion rules. In the case where Identification process give the same response that Sub-Identification one, we operate an AND rule and the system return an identity response. However, in the opposite case and if the identity returned by the Identification process doesn't exist in the kept subset, we proceed to do an OR fusion rule to keep a partition which contain potentially the searched identity. We developed this fusing scheme on the first expert. We obtain 78.5% of right identification (AND rule). In the other cases, we perform a new subset constituted from the elaborated subset issued from the clustering task and the identity returned by the Identification process. We miss only 9 query images from a set of 400 query faces. We have only 2.25% of false matching rate.

TABLE I

 I

	.		DATABASE SUBDIVISION -SEARCHING STRATEGIES
		Expert 1				Expert 2
	Train -Enrol -Test		Train -Enrol -Test
	600 -600 -400			800	-800
		Expert 3				Expert 4
	Train -Enrol -Test		Train -Enrol -Test
		1200	-400		1600	-800
	TABLE II.	EXPERT 1 DATASET PARTITIONNING
	Expert 1	1		2	Session	3	4
	Shot	1 2	Training Enrolment	Training Enrolment	Training Enrolment	Test Test

TABLE III .

 III IDENTIFICATION RATE AND TOP MATCH RANK OF DIFFERENT EXPERTS

								Identification Rate
											Top Match Rank
	Learn		Expert 1			Expert 2			Expert 3			Expert 4
	PCA Inertia	80%	85%	90%	80%	85%	90%	80%	85%	90%	80%	85%	90%
	Features sizes	44	66	105	45	69	113	46	71	119	47	73	125
	Identification Rate	77.25	80.5	84	75.13	78.5	81.38	81.5	87.5	89.5	96.13 97.63 98.88
	Top matches rank	89	77	86	108	95	100	103	133	125	43	28	21
	time : Learn (Off Line)	7.45	7.51	7.65	8.77	8.81	9.05	20.7	20.8	20.9	46	45.8	44.9
	Identification	2.38	2.6	3.08	5.45	5.95	6.9	2.38	2.66	3.21	6.23	6.54	7.36

TABLE IV

 IV

	.	STATISCTICS OF THE KEPT IDENTITIES FROM THE CLOSEST
				BINS
			Max	Min	Mean of kept identities
	K=2		126	74	109
	P=1 P=2	104	42	87 151

TABLE V .

 V PCA FEATURE SIZES OF THE FIRST EXPERT AND FOR VARIOUS INERTIA. Identification rates with various feature vector sizes for the four experts.

	PCA Inertia	21% 30% 42% 50% 60% 70% 75% 80% 85% 90%
	Feature size	1	2	4	6	11	22	30	44	66 105
	Figure 4. C-

TABLE VI .

 VI C-IDENTIFICATION AND IDENTIFICATION RATE WITHIN THE KEPT PARTITION

		TABLE VII.	IDENTIFICATION PERFORMANCES OF DISTURBED FACIAL IMAGES WITH SEVERAL DEGREES NOISE
		Number of noisy pixels		0	16	64	256	400	576	1024	2025
		% of Noise per image		0	0.4% 1.6%	6.2%	10%	14%	25%	50%
		Identification Rate		98.83	98.67 98.67	98.67	98.5	97.83	97.5	83.17
		C-Identification rate		93.67	93.33 93.33	91.83	91	90.17 83.33 78.83
		Sub-Identification rate		93.33	92.67 92.83	91.5	89.83	88.17	79	68.83
		Learn		Expert 1			Expert 2		Expert 3		Expert 4
		PCA Inertia		80%	85%	90%	80%	85%	90%	80%	85%	90%	80%	85%	90%
		Features size		44	66	105	45	69	113	46	71	119	47	73	125
	K=2	C-Identification rate Sub-Identification rate	92.25 73	92.5 75.75	92.5 78.75 70.13 90.25 90.38 90.63 73.5 75.88 76.75 80.75 91 91	91 82.5	93.3 90.2	93.5 91.7	93.8 93.1
	time : Learn (Off Line)		7.58	7.55	7.61	8.99	9.28	8.94	22	22.1	22	44.7	44.4	44.3
		Identification		1.89	2.03	2.25	3.77	4.1	4.71	2.03	2.17	2.53	4.13	4.54	5.16
	K=3	C-Identification rate		86.25	86.25	86.5	86.88 86.75 87.25	86	86.75	86.5	87.5	88	88
	P=1 Sub-Identification rate	70	72.25	75	61.25 56.25	60	56.75 58.75 59.75	60.5	62	62
	K=3	C-Identification rate		98.5	98.25	98.25 98.88 98.88 98.63	99	99	99	99.5	99.5	99.5
	P=2 Sub-Identification rate 76.25	79	82.5	74.63 78.13 80.63 81.75	86.5	89	95	97	97


Francois Trompier

Céline Bassinet

Marion Baumann

Emanuela Bortolin

Christopher I Burbidge

Cinzia De Angelis

Sara Della Monaca

Paola Fattibene

Kai Rothkamm

Rachel Smith

Overview of physical dosimetry methods for triage application integrated in the new European network RENEB

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

This work is supported by the EU within FP7 Grant Agreement No. 295513 RENEB aims to establish a sustainable European network in restrospective dosimetry. A total of 23 organisations from 16 European countries will cooperate to guarantee the highest efficiency in the processing and scoring of biological samples and measurements of mobile phone components for fast, reliable results implemented in the EU emergency management. RENEB involves for the moment 3 laboratories for EPR dosimetry and 5 for TL/OSL dosimetry. At the end of the project, more laboratories would be recruited to constitute a network with reinforced measurements capacity. Other types of materials or techniques could also be considered within the RENEB project.

Over the last years, the risk of a large scale radiological event has markedly increased. This includes possible accidents in nuclear facilities but also potential terrorist attacks against key facilities or civil targets. In both contexts, retrospective dosimetry is an essential tool to estimate an actual absorbed dose. Thus, individuals, who need extensive medical care due to severe irradiation can be identified among people who have not received high doses of ionizing radiation. In such large-scale radiological scenarios the capacity of single or few retrospective dosimetry laboratories will be overcharged . As a consequence networking has been recognized as a sensible and important element of emergency response strategy. Now a European Network of retrospective dosimetry is on the way to being realized. In addition of biodosimetry techniques, retrospective dosimetry techniques such EPR spectroscopy or luminescence has been considered. These techniques are applied on materials found in mobile phones (LCD glass, touch screen, electronic components) providing possibility of a dose estimation for a large part of the population.

F

  . Trompier 1 , C. Bassinet 1 , M. Baumann 1 , E. Bortolin 2 , C. Burbidge 3 , C. De Angelis 2 , S Della Monaca 2 , P. Fattibene 2 , K. Rothkamm 4 , R. Smith 4 European exercises for EPR and OSL techniques have been recently organized under the umbrella of the EC projects Multibiodose (Multi-disciplinary biodosimetric tools to manage high scale casualties) and RENEB, utilising the technical approaches developed in the Multibiodose project. These exercises have involved most of the European laboratories of retrospective dosimetry (12 labs for EPR and 12 for OSL), which are already constituted as a research network through the Working Group 10 'Retrospective Dosimetry' of the European Radiation Dosimetry Group (EURADOS). The results have demonstrated the possibility to correctly discriminate the different dose categories of triage (0-1 Gy, 1-2 Gy and above 2 Gy), as well as the possibility to use competences and capacities of these European laboratories in an emergency (Fattibene et al., Rad Env Biophys 2014 and Bassinet et al., Rad Meas 2014). Physical dosimetry tools (EPR/OSL/TL) can be implemented in the triage process beside the classical biodosimetry tools. The RENEB project aims to integrate these existing capacities into the future network that will be constituted at the end of the project. Results and conclusions Overview of the results of the OSL intercomparison on resistors from mobile phone http://www.reneb.eu, http://www.multibiodose.eu, http://www.eurados.org


Santiago Pantano-Calderón

Claude Baron
email: baron@insa-toulouse.fr

Jean-Charles Chaudemar
email: jean-charles.chaudemar@isae-supaero.fr

Elise Vareilles
email: elise.vareilles@isae-supaero.fr

Rob A Vingerhoeds
email: rob.vingerhoeds@isae-supaero.fr

Élise Vareilles

Regarding the COVID-19 crisis from a systems engineering perspective

Keywords: COVID-19, Crisis, Modeling, Simulation, Holistic approach

come

Regarding the COVID-19 crisis from a systems engineering perspective

INTRODUCTION

In the very beginning of 2022, humanity is still fighting the most important public health crisis of the last years, the pandemic caused by the COVID-19 (OECD 2020a;OECD 2020b). At this point, it is possible to assert that governments have settled on an universal way to reduce the impacts of the coronavirus pandemic, placing trust in vaccination plans, lockdowns and simple health recommendations [START_REF] Mallah | COVID-19: breaking down a global health crisis[END_REF][START_REF] Alfano | The Efficacy of Lockdown Against COVID-19: A Cross-Country Panel Analysis[END_REF][START_REF] Xing | Efficacy and safety of COVID-19 vaccines: a systematic review[END_REF]). An example of this is the insistent call to take booster shots of COVID-19 vaccines in order to contain the wave of infections of January 2022, presumably caused by the Omicron variant [START_REF] Abbany | COVID: Have we reached the peak of omicron infections?[END_REF]. Either by countermeasures taken or the characteristics of this variant, a far fewer number of deaths than previous waves has been observed in most of countries [START_REF] Abbany | COVID: Have we reached the peak of omicron infections?[END_REF][START_REF] Joly | COVID in Europe: France reports 'tidal wave' of new infections as records broken in Italy[END_REF]). However, around 5.5 millions of deaths were reported in the first two years of the pandemic (WHO 2022) and the virus is still threatening the stability of healthcare sector [START_REF] Joly | COVID in Europe: France reports 'tidal wave' of new infections as records broken in Italy[END_REF].

The COVID-19 outbreak forced humanity to act rapidly, even if there was not enough knowledge to make wellinformed decisions (Brinks and Ibert 2020) and, indeed, in this state of emergency, there was a necessity to act as no acting would have leaded to a worse situation [START_REF] Nazir | Study of COVID-19 mathematical model of fractional order via modified Euler method[END_REF]. This characteristics of urgency, uncertainty and threat lead the entire globe into a deep crisis that affected not only the healthcare system but also economic, WiPe Paper -Analytical Modeling and Simulation Proceedings of the 19th ISCRAM Conference -Tarbes, France May 2022 Hedi Karray, Antonio De Nicola, Nada Matta, Hemant Purohit social and political sectors [START_REF] Shinde | Forecasting Models for Coronavirus Disease (COVID-19): A Survey of the State-of-the-Art[END_REF][START_REF] De Weck | Handling the COVID-19 crisis: Toward an agile model-based systems approach[END_REF]. This means that societies, and especially power agents such as governments, are not trying to control a pure health crisis, but a systemic crisis that requires an holistic approach to respond to [START_REF] De Weck | Handling the COVID-19 crisis: Toward an agile model-based systems approach[END_REF].

Therefore, as the pandemic is still threatening society and the crisis withstand all countermeasures applied until present, it is completely necessary to find tools that allow scientists to propose the best alternatives facing public health crises. Modeling and simulation has been proven to satisfactorily replicate and predict the behavior of complex systems [START_REF] Abhishek | Weather Forecasting Model using Artificial Neural Network[END_REF][START_REF] Batstone | The IWA Anaerobic Digestion Model No 1 (ADM1)[END_REF], and during these last years, as a result of the COVID-19 outbreak, different models have been proposed to reproduce the behavior of specific aspects of the pandemic in order to understand the occurring phenomenon [START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF][START_REF] Arino | A simple model for COVID-19[END_REF][START_REF] De Weck | Handling the COVID-19 crisis: Toward an agile model-based systems approach[END_REF]. However, most of proposed models focus on its epidemiological characteristics and omit the real range of the crisis, where social and economic factors are closely involved.

For this reason, this paper has the purpose to contend the necessity of using systemic and holistic model-based approaches, not only to confront the current crisis but also to aid informed decision-making for future public health events. After this introduction the current modeling for the COVID-19 crisis is presented. In the next section, some advantages of using systems engineering methods are identified to generate a more realistic model of the pandemic, and the possibility to call systems analysis and control theory concepts is contended to better visualize the crisis.

The last section proposes a discussion and recommendations for future works.

THE MODELS FOR THE CRISIS

Modeling and simulation are tools currently in use when studying the COVID-19, as they may be able to replicate the behavior of different variables involved in its corresponding epidemiology, such as the dynamics of the transmission of the virus or its mortality. This reproduction helps scientists and governments to predict the progress of the virus in the population over time, and so, it supports the decision-making facing the emergency. In this order of ideas, models are potentially useful to anticipate infection waves and new focal points, and they can help authorities to create strategies to limit the propagation of the disease, for example, imposing lockdowns or individual quarantines, limiting the transit in borders and airports or redistributing the available vaccine doses.

Current models of the pandemic are based on both medical and non-medical parameters [START_REF] Shinde | Forecasting Models for Coronavirus Disease (COVID-19): A Survey of the State-of-the-Art[END_REF]. For example, the medical parameters are several statistical and epidemiological indicators such as the transmissibility of the virus, the incubation period, proportion of asymptomatic infections and virus lifespan [START_REF] Shinde | Forecasting Models for Coronavirus Disease (COVID-19): A Survey of the State-of-the-Art[END_REF][START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF][START_REF] Arino | A simple model for COVID-19[END_REF]. On the other hand, among the non-medical parameters, it is possible to find geographical statistics and demographic data, such as population, birth and death rates, age and gender [START_REF] Shinde | Forecasting Models for Coronavirus Disease (COVID-19): A Survey of the State-of-the-Art[END_REF][START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF]. Even if there are several parameters that can be easily identified when building a pandemic model, there are many other hidden factors that may strongly affect the transmission or mortality of the virus, and this is the main reason why the behavior of the COVID-19 should be observed from a holistic approach.

The complexity of the pandemic

There are numerous reasons why the evolution of a pandemic is difficult to model and foresee. First, the measures taken by the governments and the appearance of novel variants of the virus cause variations in the infections rate, therefore, the transmissibility of the disease is not constant over time [START_REF] Alfano | The Efficacy of Lockdown Against COVID-19: A Cross-Country Panel Analysis[END_REF][START_REF] Xing | Efficacy and safety of COVID-19 vaccines: a systematic review[END_REF][START_REF] Chowdhury | Long-term strategies to control COVID-19 in low and middle-income countries: an options overview of communitybased, non-pharmacological interventions[END_REF]). On the other hand, economic, social, cultural and political factors may be involved in the strategies proposed by authorities confronting the crisis. For instance, even if the imposition of general quarantines proved to be an effective way to reduce the transmission of the virus among people (Alfano and Ercolano 2020), the implementation of long lockdowns is an inviable alternative due to large costs not related to epidemiological factors, as it causes huge economic loses and several social and psychological problems in medium and long term [START_REF] Michalski | The Economic Impact of Different COVID-19 Lockdown Strategies in France[END_REF][START_REF] Brooks | The psychological impact of quarantine and how to reduce it: rapid review of the evidence[END_REF].

Furthermore, some cultural, demographic and social aspects may play an important role in the transmission of the virus [START_REF] Bayeh | The Social Lives of Infectious Diseases: Why Culture Matters to COVID-19[END_REF]. Cultural practices and habits, such as the population beliefs, the gender roles and the discipline and obedience of people, may influence the infectious rate. In the present pandemic, more men than women have been hospitalized or have died by COVID-19 related causes [START_REF] Cañelles López | Coronavirus: 3 datos que explican por qué la covid-19 afecta de manera diferente a hombres y mujeres[END_REF][START_REF] Jin | Gender Differences in Patients With COVID-19: Focus on Severity and Mortality[END_REF], and some authors propose that the difference of severity and mortality rates between men and women may correspond to gendered behavioral aspects and gender-segregated occupations and not to pure biological factors [START_REF] Galasso | Gender differences in COVID-19 attitudes and behavior: Panel evidence from eight countries[END_REF][START_REF] Shattuck-Heidorn | What's Really Behind the Gender Gap in Covid-19 Deaths?[END_REF]). In the same way, populations with psychological predispositions to reject scientific researches suffer bigger risks of aggravation of the emergency [START_REF] Bayeh | The Social Lives of Infectious Diseases: Why Culture Matters to COVID-19[END_REF].

Mathematical and data science techniques are largely employed to predict the progress of the pandemic and, certainly, the sources and amounts of data collected have an important role in forecasting [START_REF] Shinde | Forecasting Models for Coronavirus Disease (COVID-19): A Survey of the State-of-the-Art[END_REF]). On the basis of analytical approaches, different mathematical models have been proposed to replicate the evolution of the number of infections over time, for example, the Bats-Hosts-Reservoir-People (BHRP) model, simplified to Reservoir-People (RP) model, which is expressed in six differential equations [START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF], and the computational model on COVID-19 based on cellular automata [START_REF] Ghosh | Computational Model on COVID-19 Pandemic Using Probabilistic Cellular Automata[END_REF]. However, the main issue that we found is that most of traditional approaches used today do not fit the reality as expected since they usually concentrate only on the epidemiological aspects of the disease.

The suitability of a traditional model

In order to analyze the reliability and suitability of traditional analytical models, we tested the BHRP transmission network model, proposed by [START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF], since it is one of the nine most commonly used models based on mathematical implementations (AlArjani et al. 2022) and it is an extension of another traditional compartmental model in epidemiology, the Susceptible-Infectious-Recovered (SIR) model [START_REF] Chen | Investigation of Key Interventions for Shigellosis Outbreak Control in China[END_REF]. The major contribution of this approach stands in the consideration of the complete transmission route from the bats to the people through the seafood market in Wuhan, China [START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF]), though the model was simplified into a RP model and normalized in order to explore it more clearly. Afterwards, the normalized RP model can be used to calculate the basic reproduction number 𝑅 0 to evaluate the transmissibility of the SARS-COV2 [START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF]). This model is also capable to estimate and reproduce the dynamic of transmission of the virus by introducing several epidemiological parameters: Incubation period, duration of symptoms, fraction of asymptomatic infections and lifespan of the virus in the reservoir. A population and its birth and death rates are also required to perform a simulation.

In order to test the model, we collected the data of the epidemic curve of Bogota, Colombia, from February 26 th , 2020, date of the first reported case in the city, to June 5 th , 2020 (SALUDATA 2021). The sample frequency of the data is 1 day. The epidemic curve and the date of the implementation of the first lockdown, on March 25 th , 2020, are shown in figure 1. Following the method and the parameter values suggested in [START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF], two curve fitting processes using the method of least squares were performed to estimate the value of the normalized diffusion rate of the virus. A simulation for each curve fitting result was carried out with a step time of 1 day. To do so, and in order to soften the abrupt changes in the epidemic curve, real data was processed by calculating, for each sample, the average of the number of new symptomatic cases of three days, as shown in equation 1, where 𝐼 is the number of new symptomatic cases in the day 𝑖 after the detection of the first symptomatic case. At first, processed real data from February 26 th , 2020 to April 16 th , 2020 were used to do the curve fitting. In a second case, processed real data from April 17 th , 2020 to June 5 th , 2020 were used to perform the same procedure. The corresponding simulation results are shown in figures 2 and 3. The first round of simulation, where the normalized diffusion rate of the virus was estimated using the processed real data of the first 50 days of epidemic, resulted in a simulated behavior completely distant from reality. According to the simulation, we found that, on June 5 th , health authorities should have detected 5,156 new symptomatic cases, but in fact, there were 542 new symptomatic cases reported in Bogota on that day. This discrepancy may be explained by the omission of the lockdown imposed in the city 28 days after the detection of the first infected person, as this probably caused an overestimation of the transmissibility of the disease in the model. This was the reason why a second estimation of the normalized diffusion rate was needed, using the epidemic curve a few weeks after the lockdown was declared, in order to perform a second simulation.

𝐼 𝑖 𝑝𝑟 𝑜𝑐𝑒𝑠𝑠𝑒𝑑 =          𝐼 𝑖 𝑟 𝑒𝑎𝑙 , 𝑖 = 0 ( 𝐼 𝑖-1 𝑟 𝑒𝑎𝑙 + 𝐼 𝑖 𝑟 𝑒𝑎𝑙 )/2, 𝑖 = 1 ( 𝑖 𝑘=𝑖-2 𝐼 𝑘 𝑟 𝑒𝑎𝑙 )/3, 𝑖 > 1 𝑖 ∈ {N ∪ 0} (1)
In the second round, the normalized diffusion rate of the virus was estimated using the processed real data from the day 51 to the day 100 after the first reported case on February 26 th , 2020. This time simulation fit better the real new symptomatic cases over all the 100 days of data collected. Therefore, it was possible to notice that the model would be able to predict the evolution of the epidemic curve, at least, in short term. This was confirmed when the simulation was extended 15 days more, where the simulated data estimate 1,493 new symptomatic cases on June 20 th , 2020, and real data shows 1,397 new symptomatic cases in the city on the same date (SALUDATA 2021), i.e. on that day we found a discrepancy of 96 cases, or 6.9%. Nevertheless, when extending the simulation 15 days more, or 30 days in total until July 5 th , 2020, we clashed with a divergence of 1219 cases, or 65,6%, as simulation estimates 3,076 new symptomatic cases, whereas there were in fact 1,857 new symptomatic cases on that day in Bogota (SALUDATA 2021). previous subsection, the transmissibility of the disease is variable over time due to the health strategies introduced by governments. On the other hand, the virus itself does not remain invariant in time. So far, 12 variants of the SARS-COV2 have been detected and classified (CDC 2021b), each one having its own infection ability and mortality (CDC 2021b). Likewise, the complexity of real relationships was completely omitted in the BHRP model. Overall, this kind of traditional mathematical models, rather usual in the study of the COVID-19 pandemic [START_REF] Shinde | Forecasting Models for Coronavirus Disease (COVID-19): A Survey of the State-of-the-Art[END_REF][START_REF] Chen | A mathematical model for simulating the phase-based transmissibility of a novel coronavirus[END_REF][START_REF] Arino | A simple model for COVID-19[END_REF], are very limited and do not fulfill the fidelity expectations to support the decision-making facing the current crisis.

SYSTEMIC APPROACH OF THE PANDEMIC

After the explanation of the current crisis and the formulation of the problem, it is possible to identify three main characteristics of COVID-19 emergency. To begin with, it exhibit a global impact [START_REF] De Weck | Handling the COVID-19 crisis: Toward an agile model-based systems approach[END_REF], where society find itself out of normal functioning in all essential levels, i.e. in social, economic and heath systems (de Weck et al. 2020; Brinks and Ibert 2020). In addition, there is a strong intrinsic feedback delay when fighting the spreading of the disease, as the virus cannot be detected during its incubation period [START_REF] Winkelhake | If you're fully vaccinated, wait a few days after a COVID-19 exposure before getting tested[END_REF], and the strategies deployed by authorities are often centered in mitigating health issues in short term due to the necessity to respond urgently, omitting medium-term and long-term consequences [START_REF] Simon | Impacts of the Covid-19 lockdown and relevant vulnerabilities on capability well-being, mental health and social support: an Austrian survey study[END_REF][START_REF] Brooks | The psychological impact of quarantine and how to reduce it: rapid review of the evidence[END_REF][START_REF] Michalski | The Economic Impact of Different COVID-19 Lockdown Strategies in France[END_REF]. Moreover, there is also a strong uncertainty bound to the nature of the crisis, as the portion of infections that were not detected by the healthcare authorities is considerably large, around 75% (95% CI1, 70.6% -78.7%) in the U.S. until November 2021 (CDC 2021a). Likewise, uncertainty is bound to the complexity of the human behavior and social relationships [START_REF] Bayeh | The Social Lives of Infectious Diseases: Why Culture Matters to COVID-19[END_REF].

Consequently, in order to move towards an approach capable of replicating the first of the three characteristics of the crisis mentioned previously, i.e., its global impact, it is necessary to construct a holistic framework that takes into account all the involved forming components of society. In this sense, de Weck et al. 2020 managed to identify that there are five primary systems are involved in the COVID-19 pandemic: Biological system, social system, healthcare system, political system and economic system. Indeed, interactions between them must be equally considered. As it was stated in the previous section, models are hardly realistic whether they only consider the biological characteristics of the disease, that is to say, its epidemiology. Additionally, government decisions and economy play an important role in the evolution of the epidemic [START_REF] Alfano | The Efficacy of Lockdown Against COVID-19: A Cross-Country Panel Analysis[END_REF][START_REF] Chowdhury | Long-term strategies to control COVID-19 in low and middle-income countries: an options overview of communitybased, non-pharmacological interventions[END_REF]. Taking into account the previous conceptions, a global framework is proposed in figure 4. This holistic approach derives into a system-of-systems that allows the model to be more loyal and closer to reality. The presented framework implies that the crisis encompasses five different sub-systems, complex interactions, internal feedback loops and a distributed behavior. This ensemble of properties, in turn, indicates that the COVID-19 pandemic should be treated as a complex system. On the other hand, analytical approaches require a prior complete understanding of the system since, to apply them, a detailed description of the behavior of each involved element is needed [START_REF] Aziza | Simulating Complex Systems -Complex System Theories, Their Behavioural Characteristics and Their Simulation[END_REF]). Then, it is possible to realize that pure analytical modeling would not be an advantageous Otherwise, it is also necessary to contend with the existing feedback loop delays and the uncertainties inherent to the crisis. Alone, in its fundamental behavior, the pandemic acts like an unstable open-loop system that grows exponentially [START_REF] Karray | How control theory can help us control COVID-19[END_REF]). However, when infections are detected and health strategies are implemented, the pandemic can be seen as a traditional control system of which feedback signal and control signal are the number of new infections and the countermeasures, respectively. Moreover, control engineering methods are already in use in the containment of the pandemic, for example, when authorities declare a lockdown after the basic reproduction number 𝑅 0 reaches a threshold (BBC Mundo 2020), resembling an on-off control system. Fortunately, as many other systems, pandemics can be stabilized and controlled [START_REF] Karray | How control theory can help us control COVID-19[END_REF]).

On the other hand, regarding the mitigation plans for the COVID-19 pandemic, control theory may provide interesting approaches to respond to the crisis. According to the proposed holistic approach, there are two main feedback signals that authorities use to conceive and introduce health and economic strategies: public health and economic indicators. These feedback signals may have a delay caused by the nature of the crisis, as established in the beginning of this section. Compensating delayed feedback requires prediction, and in order to contend with it, predictive control methods, such as the Smith predictor and the Kalman filter, may be profitable [START_REF] Frank | Time Delays[END_REF].

Likewise, uncertainty can be reduced with predictive control methods, since they can estimate the non-observed variables of the system, and also with adaptive control methods, as they can adapt to different variations on the pandemic parameters over time.

CONCLUSIONS

After contemplating the way the COVID-19 pandemic has been modeled, this paper highlights the need to develop more realistic models to find effective strategies to mitigate the spread of the disease. The imposition of strong health policies led to serious economic impacts in a short time, which caused the deterioration of other forming aspects of society. Consequently, the pandemic requires a systemic approach that considers the different sectors as a whole system in order to understand its multi-level structure, feedback loops and distributed decision-making. This paper is part of a work in progress, and indeed, there are several elements in this analysis that require further elaboration. However, different tools such as systemic approaches, high-complex systems analysis and control theory may be truly useful to understand and model the occurring phenomena, and likewise, systems and control engineering may have an important role to face and mitigate the crisis.

Figure 1 .

 1 Figure 1. Curve of new symptomatic cases per day in Bogota from February 26 th , 2020 to June 5 th , 2020

Figure 3 .

 3 Figure 2. Simulation of the BHRP model using data of the first 50 days of pandemic to perform the estimation of the normalized diffusion rate

Figure 4 .

 4 Figure 4. Holistic approach of the crisis, based on the work of de Weck et al. 2020.

  to model the pandemic. However, systems engineering, and more specifically, systemic approaches may provide the most appropriate modeling methods to reproduce the behavior of the emergency (de Weck et al. 2020), as they are capable to represent a large number of nonlinear interactions, guided by objectives and not by details[START_REF] Aziza | Simulating Complex Systems -Complex System Theories, Their Behavioural Characteristics and Their Simulation[END_REF]).

1Confidence interval WiPe Paper -Analytical Modeling and Simulation Proceedings of the 19th ISCRAM Conference -Tarbes, France May 2022 Hedi Karray, Antonio De Nicola, Nada Matta, Hemant Purohit method


métier : superviseur d'effets visuels 9 . L'histoire des effets spéciaux s'enrichit, en effet, avec les transformations apportées par les pratiques numériques. Par exemple, si, dès 1908, des plaques de verre peintes ont été placées pour transformer les paysages devant la caméra (on appelle cela le matte painting), le numérique a considérablement modifié cette façon de faire puisque tout paysage peut désormais être transformé sans limite sur ordinateur 10 . Dans les dix dernières années, ces entretiens se sont multipliés à l'initiative de chercheurs qui ont incités leurs étudiants à interroger les divers opérateurs de la création audiovisuelle. C'est le cas, par exemple, du séminaire « Question d'histoire des métiers des techniques du cinéma et de la télévision », animé par Kira Kitsopanidou et Sébastien Layerle à l'Université Sorbonne Nouvelle-Paris 3. Bérénice Bonhomme a elle aussi procédé à de nombreuses interviews qui ont permis d'écrire un livre synthétisant l'évolution des métiers face aux transformations techniques des années 2000 (essentiellement le passage au numérique) 11 .

Une archéologie des métiers ?

Géraldine Poels note que l'Ina dispose de 12 millions d'heures d'émissions à écouter et à voir, dont certaines nous permettent de plonger dans le passé des techniciens de plateau. Dans ce choix gigantesque se trouve un grand nombre « d'émissions réflexives » qui étudient le fonctionnement des médias télévisuel et radiophonique. Ainsi, l'émission télévisée Micros et caméras, des années 1960 et 1970, montre de façon précise les problèmes qui se posaient pour la réalisation des programmes. La mise en perspective comparative des différentes technologies s'inscrit dans le vaste projet d'archéologie des médias en développement au sein de la recherche universitaire. Un numéro des Cahiers Louis Lumière fait le point sur ce sujet en abordant autant les questions du son que de l'image 12 . Ce type de recherche joue un rôle majeur dans la mise en valeur des ressources de l'Ina. Au Québec, l'analyse de l'intermédialité (André Gaudreault, Viva Paci) a poussé assez tôt vers l'étude comparative des techniques audiovisuelles 13 . Dans les travaux récents en cours, on peut aussi citer des doctorants qui étudient des supports oubliés comme le scopitone. Ce procédé permettant de Les métiers de l'animation et les appareils inventés pour faire du dessin animé restent aussi à explorer. Ainsi, encore peu de textes ont été écrits sur l'Animographe, une machine utilisée à l'ORTF et qui a servi notamment à créer la série des Shadoks16 . Considérer l'évolution des pratiques de la vidéo, qu'il s'agisse de vidéo légère pour les appropriations militantes et plasticiennes ou de vidéo lourde pour la télévision, peut permettre d'aborder l'histoire du matériel sous l'angle de la prise de vues, du montage et de la diffusion. Les archives de l'Ina (audiovisuelles ou écrites) ont, elles, permis d'étudier la transformation des stratégies des chaînes et montré que le contrôle de la direction de l'ORTF sur ce qui est diffusé est devenu plus fort quand on est passé de la dramatique diffusée en direct à des émissions enregistrées ou à des téléfilms17 . Le matériel et la profession changent aussi18 . L'identité professionnelle, le statut des travailleurs de la télévision et leur rapport au monde du cinéma se transforment en fonction des passerelles établies, des pratiques de tournage ou des attitudes de la hiérarchie Les inventaires des compagnies comme Pathé permettent enfin de dater l'apparition d'un appareil ou la mise en construction en usine. L'analyse des ventes de l'entreprise est essentielle pour apprendre quand un projecteur a été effectivement mis en service dans les salles de cinéma. Parfois des machines sont développées mais n'arrivent pas jusqu'à la production en série. Stéphanie Salmon souligne que les archives Pathé constituent des sources fondamentales pour étudier l'industrie cinématographique. On peut en effet observer l'intégralité de la chaîne des métiers du cinéma, depuis la fabrication de la pellicule jusqu'à la projection dans les salles de cinéma, en passant par toutes les techniques de prise de vue, de son, ainsi que le tirage de copies en laboratoire. Les documents des laboratoires révèlent à quel point il était délicat de réussir l'étalonnage d'un film. Des teintes d'un précédent tirage pouvaient rester dans le fond d'une cuve mal lavée et une copie pouvait sortir dans des couleurs bien éloignées de ce qui était prévu. Sur le dosage chimique des couleurs et les métiers liés à la production de film en couleur, la thèse récente de Céline Ruivo a ainsi permis de faire le tri entre légende et réalité à propos de la firme Technicolor24 .

De nouveaux sujets de recherche ?

Une histoire des techniques et des métiers passe par l'analyse des traces de tournage : photos, comptes rendus, mémos, rapports, demandes de matériel, échanges divers entre la production et l'équipe. Stéphanie Salmon incite les chercheurs à étudier les photos de plateau en observant en détails les clichés pris sur le vif pendant les tournages et, surtout, pendant les pauses. Le matériel qui apparaît sur les photos contredit parfois les souvenirs des techniciens, des réalisateurs ou des acteurs. Quelles étaient les caméras utilisées pour tourner ? Étaientelles toujours blimpées (insonorisées) au cours des années 1930 ? Comment le plateau s'organisait-il ? Où se trouvait l'ingénieur du son ? A quels types de micros avait-on recours ? Une observation globale des métiers du cinéma sur une période donnée est possible, comme l'a montré la thèse de Morgan Lefeuvre : cette étude socio-historique des professions du cinéma décrit aussi bien les conditions de travail, les déplacements quotidiens, que les statuts sociaux ou les rapports hiérarchiques au sein des studios 25 .

Pour développer de nouvelles recherches il faut également s'appuyer sur des connaissances anciennes. Géraldine Poels souligne la nécessité de comprendre le fonctionnement des appareils devenus obsolètes avec le numérique. Peu de jeunes étudiants ont déjà observé des bandes magnétiques. L'Ina garde des machines anciennes en état de marche pour pouvoir effectuer des transferts et restauration de supports révolus, mais ces appareils permettent aussi de faire redécouvrir le « matériel d'antan ». Très peu de recherches ont été menées sur les magnétophones et leur utilisation dans l'audiovisuel, par exemple 26 . Quand des travaux évoquent des bandes magnétiques, il s'agit le plus souvent d'analyser les choix effectués au montage et au mixage 27 . Tous les appareils ayant servi au son des films restent à étudier. Si un numéro de la revue 1895 est consacré aux métiers du cinéma, les différents articles ne font qu'effleurer des sujets qui demanderaient chacun des années de recherche 28 . On note néanmoins le développement international des sound studies. Des colloques et des publications permettent de comprendre l'archéologie sonore du cinéma, du théâtre et de la télévision 29 .

Un métier en particulier mérite d'être reconnu et étudié : le ou la documentaliste. Géraldine Poels explique que l'ORTF employait des documentalistes professionnels qui, à l'aide de fiches, pouvaient retrouver des émissions anciennes. Des extraits de ces reportages pouvaient être réemployés dans de nouvelles émissions. Cette réutilisation des extraits anciens de la télévision, fondamentale pour le montage de nombreux sujets, est comparable à celle des stock-shots au cinéma. Comment retrouver des images précises dans des millions d'heures 25

«

  projeter des chansons » dans les bars a lancé la production d'appareils ressemblant à des juke-boxes (appelés comme les courts films en 16 mm illustrant les chansons à la mode, des scopitones) qui se sont vendus, en grand nombre, en Europe dans les années 1960 (cf. la thèse d'Audrey Orillard : Scopitone. Histoire culturelle du télé-box et de la chanson filmée yéyé (1959-2010) 14 ). Actuellement en cours d'écriture, une autre thèse élargit le propos, toujours dans le cadre d'une histoire culturelle d'un média populaire. Robin Cauche y développe ses recherches sur la chanson écrite et projetée, depuis les plaques de lanternes magiques au XVIII e siècle jusqu'aux lyric videos produites en masse par des amateurs sur Internet, en passant par les scopitones 15 . Ces thèses peuvent aider à comprendre la longue lignée des médias d'une même série, croisant ici chansons et images depuis le XIX e siècle jusqu'à la transmission sur Internet. Elles soulignent la continuité de phénomènes médiatiques au-delà du changement de support technique. La Cinémathèque française et l'Ina mettent à disposition leurs ressources et accueillent très favorablement les recherches de ce type.

  photographies d'appareils et des fiches descriptives. Récemment, elle a bénéficié d'une donation de la famille d'un représentant en Pathé-Baby tout particulièrement intéressante parce qu'elle comporte les schémas techniques détaillés des divers appareils. Ces fiches techniques permettent, par exemple, de comprendre aujourd'hui comment fonctionnaient les amplificateurs qui servaient à diffuser le son des films. Ces éléments sont fondamentaux pour aider à la restauration des films, et surtout des appareils. Le Pathé-Baby était conçu pour être bon marché et fonctionner de façon très simple, loin de la sophistication du matériel professionnel. Il est nécessaire d'étudier les différents types d'appareils et les usages qui en sont faits. Tous les conservateurs de matériels soulignent qu'il faut pouvoir faire fonctionner les machines pour bien savoir les utiliser. Cela rejoint le travail de l'ingénieur et du restaurateur de film belge Jean-Pierre Verscheure qui, dans son centre d'étude sur les techniques cinématographique, Cinévolution, recherche et restaure les anciens appareils, permettant de la sorte une projection la plus proche possible de celle qui existait à l'époque de la sortie des films. Il a par exemple reconstitué le « son réel » (autant que faire se peut) des films Vitaphone, avec leurs amplificateurs particuliers, leurs haut-parleurs étonnants et leurs tourne-disques d'époque 22 . Ce son n'a que peu à voir avec celui des films d'aujourd'hui dans les salles actuelles. Les recherches en histoire du cinéma demandent un minimum d'observation des techniques. Les changements de formats de pellicule ont des retombées sur la réception des films. Une projection désanamorphosée en Cinémascope-Hypergonar sur un écran gigantesque donne des sensations bien différentes de celle en 1,33 sur un écran presque

  Morgan Lefeuvre, De l'avènement du parlant à la Seconde Guerre mondiale : histoire générale des studios enFrance 1929-1939, thèse sous la direction de Michel Marie, Université Sorbonne Nouvelle-Paris 3, 2016.26 Les thèses sur le sujet de la bande magnétique sont plutôt en physique ou en mécanique comme pour Frédéric Souchon, Tribologie d'un enregistreur magnétique hélicoïdal : contact tête silicium/bande magnétique, thèse sous la direction d'Yves Berthier, INSA Lyon, 1997. 27 C'est le cas au sujet d'Orson Welles, quand François Thomas a comparé ses oeuvres à la radio et au cinéma. François Thomas, La Composition sonore dans le cinéma d'Orson Welles et ses rapports avec son oeuvre radiophonique et théâtrale, thèse sous la direction de Jacques Aumont, Université Sorbonne Nouvelle-Paris 3, 1997. 28 Par exemple l'article sur les ingénieurs du son reste très succinct et demanderait des développements ultérieurs. Martin Barnier, « Les premiers ingénieurs du son français », 1895 Revue d'histoire du cinéma, n°65, hiver 2011 (février 2012), pp. 200-217. 29 Les travaux de Rick Altman, de Jonathan Sterne ou les colloques dirigés par Giusy Pisano et Jean-Marc Larrue ont fait avancer la recherche dans ce domaine, mais il reste beaucoup à faire. Jonathan Sterne (dir.), The Sound studies reader, New York, Routledge, 2012 ; Jean-Marc Larrue et Giusy Pisano, Les Archives de la mise en scène. Hypermédialité du théâtre, Lille, Septentrion, 2014.d'enregistrement de la télévision ou de la radio ? Les documentalistes actuels et leur base de données poursuivent le travail commencé, il y a très longtemps, avec des fiches cartonnées. L'archivistique et la bibliothéconomie ne datent pas de l'âge du film puisque les systèmes d'indexation pour les livres ont été mis au point au XIX e siècle. Le système Dewey, toujours utilisé dans les bibliothèques du monde entier, date de 1876, vingt ans avant les premiers tournages réguliers de films, mais ce procédé est contemporain des premiers enregistrements sonores sur des rouleaux de cire. Il reste aussi à faire l'histoire des notices des documentalistes de l'audiovisuel et l'évolution d'un métier qui est passé lui aussi par la numérisation et l'informatisation. La BNF, précise Alain Carou, a gardé elle aussi une collection d'appareils de façon à montrer à tous les chercheurs, les jeunes documentalistes, conservateurs et bibliothécaires l'évolution des procédés d'enregistrement des sons et des images ainsi que les systèmes de restitution. De la lecture sur cylindres de cire aux cassettes vidéo numériques, l'évolution des appareils s'est faite de manière relativement lente. Aujourd'hui pourtant, la transformation du matériel n'est plus visible à l'oeil nu. Pour comprendre les modifications d'un logiciel, il faut être informaticien alors que le passage d'un pavillon de phonographe à un haut-parleur en carton (inventé par Louis Lumière 30 ) est compréhensible par un néophyte. Alain Carou évoque la « fin de la transparence technique » : avec la fin des techniques analogiques disparaissent également les gestes qui accompagnaient chaque appareil. En conclusion, on peut remarquer que de nombreux chantiers de recherche sont en cours dans le domaine de l'histoire des métiers de l'audiovisuel et des machines de captation et de restitution des images et des sons. Des expositions ou des colloques se penchent sur l'utilisation du matériel et son histoire, comme à la Cinémathèque Française, la manifestation « De Méliès à la 3-D : la machine cinéma » 31 . Un projet, dans le cadre du Labex Arts-H2H, incluant plusieurs colloques internationaux autour de l'articulation « Machines, magies, médias », ouvre sur un vaste ensemble de recherches 32 . Le champ des études techniques 30 Louis Lumière a imaginé le système d'une membrane cartonnée qui vibre pour transmettre les sons en 1908. Il a déposé immédiatement un brevet pour ce diaphragme en papier. Le procédé a été commercialisé par Gaumont dans les années 1920 et par d'autres compagnies. On trouve un bel exemplaire de 1928 dans les collections de la Cinémathèque française (˂www.cinematheque.fr/fr/catalogues/appareils/collection/haut-parleurcnc-ap-97-867.html˃). 31 Exposition programmée à la Cinémathèque française du 5 octobre 2016 au 29 janvier 2017, accompagnée d'un colloque sous la direction d'André Gaudreault (Université de Montréal), Laurent Mannoni (Cinémathèque française), Gilles Mouëllic (Université Rennes 2) et Benoît Turquety (Université de Lausane), décembre 2016. 32 Voir le site du programme de recherche « Les Arts trompeurs : Machines, magies, médias » : ˂www.lesartstrompeurs.labex-arts-h2h.fr/en˃. Un colloque a eu lieu à Cerisy en août 2016, sur les rapports entre la magie et les médias. Un autre spécifiquement sur la stéréoscopie a eu lieu en septembre 2016 : Stéréoscopie et s'élargit avec un regard nouveau sur les appareils, qui fascinaient déjà les pionniers de l'histoire du cinéma. Aujourd'hui, avec de nouveaux angles d'attaque (comme les sound studies) et sans doute à cause du passage de l'analogique au numérique, les centres d'archives jouent un rôle encore plus important dans l'observation des métiers et des techniques. Il y a à peine vingt-cinq ans, constatait Éric Le Roy dans une remarque citée en introduction à ce chapitre, les collections n'étaient ni consultables ni divulgables. En 2017, au contraire, on peut tout consulter, dans la mesure où les documents demandés (film ou non-film) ne sont pas détériorés. Restent néanmoins des problèmes d'accessibilité aux fonds. Joël Daire souligne qu'il y a encore beaucoup de travail à faire entre institutions, par exemple, pour la mise au point d'une plateforme nationale du patrimoine cinématographique, même si les progrès sont très nets ces dernières années. Plusieurs chercheurs demandent s'il serait possible d'avoir accès au matériel lui-même pour savoir par exemple comment se manipulait une caméra, comment se tournait une manivelle, mais la conservation des fonds reste encore pour l'instant la priorité, une priorité qui gêne ce type de manipulation des objets. Le numérique aide par ailleurs grandement les recherches. La possibilité actuelle de consulter en ligne les revues anciennes numérisées est un confort qui n'avait jamais été proposé aux historiens par le passé. Toutefois, il n'est pas sans importance que quelques périodiques soient encore consultables sur papier à la fondation Jérôme Seydoux-Pathé : cela favorise un autre type de lecture par rapport à celle qui se fait sur ordinateur. Des formats rares ou des films réalisés de façon totalement marginale, par des amateurs, des artistes ou des filmeurs solitaires, sont maintenant accessibles dans les archives cinématographiques, et particulièrement dans les cinémathèques régionales comme la Cinémathèque de Grenoble, la Cinémathèque des Pays de Savoie, la Cinémathèque de Bretagne, la Cinémathèque de Toulouse ou encore les Archives audiovisuelles de Monaco. On le voit, de nouvelles perspectives s'ouvrent ... Aux chercheurs de s'en emparer. illusion (ENS Louis-Lumière et Fémis).

9

  Réjane-Hamus Vallée et Caroline Renouard, Superviseur des effets visuels, Paris, Eyrolles, 2016. 10 Réjane Hamus-Vallée, Peindre pour le cinéma. Une histoire du matte painting, Lille, Presses du Septentrion, 2016.

11

Bérénice

Bonhomme, Techniques du cinéma : image, son, post-production, Paris, Dixit, 2011. 12

Gérard Pelé et Giusy Pisano, Archéologie des médias, dossier de la revue numérique de l'ENS Louis-Lumière, Cahiers Louis Lumière, n°10, décembre 2016.

13

André Gaudreault et Philippe Marion, La Fin du cinéma ? Un média en crise à l'ère du numérique, Paris, Armand Colin, 2013 ; Viva Paci, La Machine à voir. À propos de cinéma, attraction, exhibition, Lille, Presses du Septentrion, 2012.

Tout le monde s'accorde sur ce point : faire l'histoire des techniques et des métiers du cinéma et de l'audiovisuel exige de recourir à des sources spécifiques, des documents d'archives mais aussi des appareils. Mais quels fonds et quels objets relatifs à ce domaine conservent et rendent accessibles, aujourd'hui, en France, les institutions à vocation patrimoniale et scientifique ? Quelles sont les recherches déjà engagées sur ce type de sources ? Quelles pistes ouvrent la voie à de nouvelles recherches ? Dans le cadre du colloque « Métiers et techniques du cinéma et de l'audiovisuel : approches plurielles (objets, méthodes, limites) », une table ronde réunissant les responsables de plusieurs institutions ainsi que des chercheurs, a permis de faire le point sur ces questions 1 . Si l'accès à ce type d'archives est relativement récent, depuis une dizaine d'années, leur consultation a été facilitée et les fonds se sont constamment enrichis. La numérisation, la mise en ligne de photographies d'appareils, de plaques de lanternes magiques, permettent à chacun de découvrir de chez soi les fonds patrimoniaux conservés dans plusieurs collections. Des conférences, dans le cadre du Conservatoire des techniques cinématographiques, créé en 2008, ont permis de faire connaître les richesses du Musée du cinéma de la Cinémathèque française et incité à faire de nouveaux dons 2 . Ce Conservatoire a en effet une triple mission : étudier, inventorier, restaurer et valoriser ses collections, aider à l'écriture de l'histoire technique du cinéma et continuer la collecte d'appareils anciens et récents. Il se donne aussi comme objectif d'enseigner l'histoire technique du cinéma, une histoire souvent méconnue, en organisant, un vendredi par mois, une conférence assurée par des spécialistes. L'organisation de grandes expositions à la Cinémathèque française, mais aussi dans de nouveaux lieux comme la Fondation Jérôme Seydoux-Pathé, fonctionne également comme un appel aux dons. Les sources se font plus nombreuses et la possibilité d'observer les appareils existe désormais, mais il faut reconnaître que cette ouverture vers les chercheurs a mis du temps à se mettre en place. Il y a vingt-cinq ans, remarque Éric Le Roy, la plupart des documents des archives du film n'étaient ni consultables ni divulgables. 1 Cette table ronde organisée le 12 février 2016, intitulée « Problématique des sources » et animée par Martin Barnier, a réuni les participants suivants : Alain Carou (Conservateur au Département de l'Audiovisuel de la Bibliothèque nationale de France, responsable du Service Images animées), Joël Daire (directeur délégué du patrimoine de la Cinémathèque française), Anne Gourdet-Mares (responsable des appareils et des ateliers de la Fondation Jérôme Seydoux-Pathé), Éric Le Roy (chef du Service Accès Valorisation et Enrichissement des Collections aux Archives françaises du film du CNC et président de la Fédération Internationale des Archives du Film), Géraldine Poels (responsable de la valorisation scientifique à l'Ina) et Stéphanie Salmon (directrice des collections historiques en charge des expositions de la Fondation Jérôme Seydoux-Pathé). 2 En partenariat avec les Universités Paris 1, Paris 3, Paris Diderot et Paris-Ouest Nanterre, la Commission supérieure technique, La Fémis, l'École nationale supérieure Louis-Lumière et Ina SUP. Voir en ligne ˂cinematheque.fr/cycle/le-conservatoire-des-techniques-cinematographiques-77˃ (consulté le 1 er mars 2017).

les années 2010) y est pour beaucoup : mis au rebut, ces appareils ont pu être récupérés dans des collections. Mais il y a aussi l'effort de toutes les institutions pour développer l'accessibilité à leurs fonds et enrichir leurs collections. Les archives « non-film » (qui incluent les appareils, le matériel publicitaire comme les affiches ou les photos, tous les documents de production, les revues, journaux spécialisés en cinéma ou télévision, etc.) sont de plus en plus nombreuses et de plus en plus numérisées. Joël Daire et Éric Le Roy expliquent que le CNC et la Cinémathèque française « vident régulièrement des caves ». Hors de ces institutions traditionnelles, on peut citer le travail exemplaire mené par Stéphane Lerouge au sein d'un label discographique qui réédite, et parfois édite pour la première fois en disque ou CD, des musiques de film (cette collection de bandes originales de films a débuté en 2000 4 ). Depuis plusieurs années, lors de ses interventions dans le cadre de Master Class sur la musique de film, au Festival Lumière de Lyon, il a expliqué comment il insistait auprès de certains compositeurs ou de leur famille pour regarder dans leur cave et voir s'il n'y avait pas de trésors. Reste qu'il faut souvent un gros travail de restauration pour rendre audibles les bandes magnétiques ou autres supports retrouvés dans des conditions de conservation très aléatoires. Mais cela en vaut la peine : Stéphane Lerouge raconte ainsi comment Agnès Varda lui a confié des mini-cassettes, datant des années 1960, sans trop savoir ce qu'elles 3 G-Michel Coissac, Histoire du cinématographe de ses origines à nos jours, Paris, éditions du Cinéopse, 1925. 4 CD édités par le label Emarcy de Universal Music Jazz France.

« Nous sommes deux soeurs jumelles » des Demoiselles deRochefort (1967) : Jacques Demy chante avec Michel Legrand au piano, ce dernier proposant des versions complètement différentes à chaque fois. Cette archive sonore montre le travail de création en train de se faire. Le métier de compositeur peut ainsi être analysé en détail grâce à ce document unique. Entre autres stocks de films récupérés, Éric Le Roy raconte que les Archives françaises du film du CNC ont eu l'occasion de vider la cave du cinéaste José Bénazéraf, réalisateur et producteur de cinéma indépendant connu pour ses films politiques, érotiques et pornographiques et que dans les bobines ainsi retrouvées figuraient quatre montages complets et très différents d'un même film. Tous les types de films sont dignes de figurer dans les archives et tous contribuent à écrire l'histoire du cinéma et de ses métiers. Ce type de source permet en particulier de comprendre les hésitations du réalisateur et de l'équipe de montage. Le travail du monteur ou de la monteuse s'analyse alors en observant les modifications et les repentirs. Le CNC conserve également un grand nombre de chutes. Ces bouts de film éliminés représentent des documents exceptionnels pour appréhender les métiers du montage et du son, mais également le travail des acteurs puisqu'ils montrent différentes manières de jouer des dialogues identiques. On peut également étudier les diverses approches d'une mise en scène à partir des traces de tournage finalement abandonnées. Insistons : ces éléments historiques ne sont pas uniquement à penser comme des bonus potentiels de DVD, il s'agit bien de sources fondamentales pour la recherche historique. Les bouts d'essai, les tests de lumière ou de couleur, montrent également l'évolution technique et le maniement subtil des appareils par les chefs opérateurs, les pointeurs, les cadreurs, les machinistes … Parmi les essais techniques disponibles aux Archives françaises du film du CNC, notons les tests provenant de la société Rouxcolor (le fils d'un des inventeurs a donné ce qu'il avait pu récupérer des archives familiales). Dès 1930, les frères Roux ont en effet mis au point un système, par procédé additif, qui permettait de filmer en couleur à partir d'une pellicule noir et blanc 5 . Le Rouxcolor a été utilisé pour le tournage de quelques-uns des premiers films français en couleur, notamment pour La Belle Meunière de Marcel Pagnol (1948) 6 . L'histoire des techniques se fait donc parfois au hasard des donations. 5 Pascal Martin, « Le Rouxcolor : un procédé additif de reproduction des couleurs », 1895. Mille huit cent quatre-vingt-quinze [En ligne], 71 | 2013, mis en ligne le 01 décembre 2016, consulté le 16 janvier 2017. URL : ˂http://1895.revues.org/4791˃ ; DOI : 10.4000/1895.4791. 6 Alain J. Roux et Pascal Martin, « Le Rouxcolor : descriptif technique et histoire de son inventeur », 1895. Mille huit cent quatre-vingt-quinze [En ligne], 71 | 2013, mis en ligne le 01 décembre 2016, consulté le 15 janvier Les Archives françaises du film du CNC possèdent également ce qui reste des tests menés, dans les années 1920, par le professeur Henri Chrétien pour le procédé d'anamorphose Hypergonar sur lequel reposera le développement du format Cinémascope ; une partie de ce matériel avait été détruit avant que le CNC ne s'y intéresse, regrette Éric Le Roy 7 . L'histoire des techniques se fait avec des manques, des trous, mais il faut aussi valoriser les archives qui possèdent ces documents rares. Recherches sur les métiers et les appareils Sur l'ensemble des doctorats en cours à l'Université, très peu de thèses se préparent actuellement sur l'histoire des techniques ou des métiers. Les responsables des institutions préservant ce patrimoine regrettent que peu de chercheurs ou d'étudiants en Master ne s'intéressent à ce domaine malgré son incroyable richesse. Plusieurs intervenants de la table ronde témoignent néanmoins de projets actuels. Alain Carou évoque ainsi l'exemple du séminaire « Vidéo des premiers temps » organisé avec Hélène Fleckinger et Sébastien Layerle 8 , soulignant la grande complémentarité entre chercheurs et conservateurs. Le travail scientifique et la collecte patrimoniale sont dans ce cas menés simultanément. Si l'analyse s'appuie sur des bandes vidéo anciennes, numérisées et parfois restaurées, des archives et des témoignages oraux, elle favorise également la collecte de sources complémentaires. Ce type de séminaire est ainsi l'occasion d'étudier l'évolution des supports techniques et des pratiques sociales et culturelles. Actuellement, de nombreuses opérations d'enregistrements audio et vidéo sont en cours pour permettre de conserver la mémoire des métiers du cinéma et de la télévision. Des groupes d'étudiants de la Fémis filment ainsi de longs entretiens avec des techniciens à la retraite ou en activité sur les pratiques anciennes ou récentes. De la même façon, à la demande de la Commission paritaire nationale emploi et formation de l'audiovisuel (CPNEF-AV) qui a commandité ces films pour l'Observatoire des métiers de l'audiovisuel, Réjane Hamus-Vallée réalise des entretiens avec des représentants de différents métiers du cinéma. Depuis 2012, six ou sept entretiens sont ainsi mis en ligne chaque année. Certaines de ces discussions, animées par Caroline Renouard, ont aidé à l'écriture à quatre mains d'un ouvrage sur un nouveau 2017. URL : ˂http://1895.revues.org/4788˃ ; DOI : 10.4000/1895.4788 8 On pourra se reporter au carnet de recherches en ligne : ˂earlyvideo.hypotheses.org˃

Audrey Orillard, Scopitone. Histoire culturelle du télé-box et de la chanson filmée yéyé, sous la direction de Myriam Tsikounas, thèse soutenue à l'Université Paris 1 Panthéon-Sorbonne, 2014.

Robin Cauche, Des lanternes magiques aux lyric videos : la chanson écrite projetée (XIX-XXI e siècles), thèse en cours à l'Université Lumière Lyon 2 et à l'Université de Montréal, en cotutelle, sous la direction de Martin Barnier et celle d'André Gaudreault, avec une aide de la Cinémathèque française.

Sébastien Denis, Les Shadoks. Histoire, esthétique et pataphysique, Paris, INA, 2016.

Jérôme Bourdon, Histoire de la télévision sous De Gaulle, Paris, Anthropos / INA, 1990, réédition augmentée, Paris, Presses des Mines, 2014.

Jérôme Bourdon, « Les réalisateurs de télévision. Le déclin d'un groupe professionnel », Sociologie dutravail, vol.35, n°4, octobre

1993, pp. 431-445.

Kira Kitsopanidou, L'Innovation technologique dans l'industrie cinématographique hollywoodienne : le cinéma-spectacle des années 1950, une mise en perspective des stratégies liées à l'Eidophor et au Cinemascope, thèse sous la direction de Laurent Creton, Université Sorbonne Nouvelle-Paris 3, 2002.

Céline Ruivo, Le Technicolor trichrome : histoire d'un procédé et enjeux de sa restauration, thèse sous la direction de François Thomas, Université Sorbonne Nouvelle-Paris 3, 2016.

En même temps, de nouvelles méthodes et de nouvelles approches ont vu le jour. On a ainsi compris que l'objet « caméra », par exemple, ne pouvait être vraiment étudié qu'en le recontextualisant en lien avec les techniques et les métiers. Or l'histoire des métiers du cinéma ne s'est développée que depuis une période récente. De son côté, l'étude des techniques qui a été un élément déclencheur de l'histoire du cinéma, avec l'ouvrage pionnier de Georges-Michel Coissac 3 , connaît actuellement un regain de vigueur grâce aux nouvelles sources et aux nouvelles approches. Comme le montrent des thèses récentes, l'histoire des appareils, des techniques et des métiers du cinéma est en pleine évolution.

Vider les caves

Les occasions pour les chercheurs de trouver des fonds, souvent très riches, sont de plus en plus nombreuses. Joël Daire fait remarquer qu'il y a aujourd'hui plus de 6 000 appareils dans les collections de la Cinémathèque française, c'est-à-dire 3 000 de plus qu'il y a dix ans. Le passage assez brutal au numérique qui a rendu obsolète un certain nombre de machines (dans