text:
Talk:Depth of field

Hyperfocal in the "Same Picture" section
Assuming a lens with focal length and f-stop both modified by the same sensor format conversion ("crop factor"), I get the part where the equivalence breaks down as macro magnification becomes a big deal. But I don't understand the part about the equivalence breaking down at "as distance approaches the hyperfocal distance for the smaller format (the DOF of the smaller format approaches infinity)". As I calculate it, assuming also-scaled CoC, the hyperfocal distance should be the same for both formats. What am I missing? Thanks! Matthew Miller (talk) 02:45, 25 March 2011 (UTC)

 * What you're missing is that that comment is being applied to the condition stated as "With the same f-number." Afterward, the f-number ratio that makes the DOFs equal is computed, and that works fine at distance, as you note.  But the DOF ratio itself doesn't work so well when one of the DOFs can approach infinity while the other doesn't.  There might be a better way to put all this to avoid the problem, so feel free to propose a rewrite (be bold, and we'll jump in and fix it we don't like it).  Dicklyon (talk) 03:32, 25 March 2011 (UTC)

 * Our DoF comparisons (like everyone else’s) make use of approximations at near and far distances; unlike most other sources, even Stroebel, we clearly describe what the simplifying approximations are at the beginning of the subsection. One is that the distance is much less than hyperfocal, so that as the hyperfocal distance is approached, the comparisons are no longer valid. We assume that focal length and CoC both scale with format; however, because the hyperfocal distance is given by

 * $$H = \frac {f^2} {Nc} + f \,,$$

 * it is not the same for both formats, but rather scales approximately with format. I guess both Dick and I concede that the current wording may require a second read; however, at least we state what most other sources (except perhaps Bob Atkins) simply ignore. JeffConrad (talk) 07:49, 25 March 2011 (UTC)

 * Perhaps what’s not as obvious as it seems to me: the comparison becomes invalid when the magnification in either format approaches unity or when the distance approaches hyperfocal in either format. Because we assume magnification is proportional to format size, magnification approaches unity in the larger format first; because the hyperfocal distance is approximately proportional to format size, the distance approaches hyperfocal in the smaller format first. Perhaps we could state this, although to me, what we currently say in the article is more digestible than how I’ve just described it. JeffConrad (talk) 22:30, 25 March 2011 (UTC)

DOF - Increases vs Decreases
Two of my previous edits were reverted on the basis that they are incorrect, namely changing "increases" to "decreases" in the Effect on Lens Aperture section. The way the facts are presented contradict information elsewhere in the article.
 * Opening Paragraph (bold added by me for emphasis) "In some cases, it may be desirable to have the entire image sharp, and a large DOF is appropriate. In other cases, a small DOF may be more effective, emphasizing the subject while de-emphasizing the foreground and background."

 * Effect on Lens Aperture Section (bold added by me for emphasis) "Reducing the aperture diameter (increasing the f-number) increases the DOF; however, it also reduces the amount of light transmitted, and increases diffraction, placing a practical limit on the extent to which DOF can be increased by reducing the aperture diameter."

This contradicts the first paragraph. From what I understand of DOF (and the first paragraph) is that put simply, a larger (deeper) DOF means more of the scene is in focus. A smaller (shallower) DOF means only a specific range of objects will be in focus. So by reducing the aperture diameter, it brings more things into focus which would mean it INCREASES the DOF. But the Effect on Lens Aperture paragraph states otherwise. Please correct me if I am misunderstanding DOF or am missing something here with aperture sizes.

Also, I was told my edits were unsourced. I did not state any specific facts or impart any new information to the article, I was merely making it consistent. How would one suggest I have sourced that better? Hergio (talk) 18:19, 28 December 2010 (UTC)

 * I don't see any such article edit under your contribs. Can you link the diff and quote what you changed it to.  The text you bolded above seems to be correct and consistent with what you're saying when you state "reducing the aperture diameter, it brings more things into focus which would mean it INCREASES the DOF", so it's not clear what you would have changed.  Dicklyon (talk) 19:28, 28 December 2010 (UTC)

 * Edits were apparently made without logging in (using IP address 69.205.119.161). JeffConrad (talk) 02:23, 29 December 2010 (UTC)

 * There is no contradiction between the two paragraphs quoted above. The first mentions situations for which large or small DoF may be appropriate but does not discuss how to control DoF; the second describes the effect of aperture on DoF without discussing whether large or small DoF is appropriate. The edits contradicted the well-established inverse relationship between aperture diameter and DoF, were challenged as incorrect, and thus required support from a reliable source. But the main objection was that the change was incorrect, which is why I (and I presume Kleopatra as well) reverted immediately, and asked for an explanation before making the edits again. JeffConrad (talk) 02:23, 29 December 2010 (UTC)

Hyperfocal distance depth of field using EasyTimeline
The chart is an interesting illustration, but it has several issues:
 * There seems to be a confusion of aperture and numerical aperture; as Numerical aperture clearly indicates, at infinity,
 * $$N \approx \frac {1} {2\mathrm{NA}} \,,$$
 * and even then, the small-angle approximation breaks down for short-focus lenses.

 * The symbol N is used to indicate aperture (f/N), whereas in this article and similar treatments, it’s used to indicate the denominator of that fraction (e.g., “N1: f/8” should be “N1: 8”).
 * I doubt that it’s obvious to most readers that the near limit of DoF for infinity focus is H − f (I had to think for a minute), though perhaps this simply suggests that we should mention it in this article.
 * The WLs to Exposure (photography) and Distance seem a bit off the wall for this context.
 * The chart seems to imply the definition of hyperfocal distance used in this article, e.g.,
 * $$H = \frac {f^2} {NC} + f \,,$$
 * yet illustrates Hyperfocal distance using the same symbol H. The phenomenon holds only for the approximate hyperfocal distance
 * $$H \approx \frac {f^2} {NC}\,.$$

I also wonder if the chart is as appropriate here as it is in Hyperfocal distance. The bulk of the illustration is the effect of successive values of H/x; though it’s interesting, it usually isn’t useful in practical photography.
 * Because a larger version of the chart is not available, the text is quite small and hard to read, especially with the bunching up of the text of the headers in the stub columns (e.g., the first would be much easier to read if it were “f1: 50 mm, N1: f/8” rather than “f1:50mm N1:f/8”). Slightly larger text would also help, but I recognize that this could make the chart unacceptably wide.
 * A minor issue: quantity symbols H, f, and N should be in italics, as I’ve shown them.

Some of the comments are largely personal preference, but at the very least, the outright errors should be corrected if this chart is to remain here or in Hyperfocal distance. JeffConrad (talk) 00:34, 2 June 2011 (UTC)

I’ve addressed most of the easy-to-fix issues. The WLs to Exposure (photography) and Distance remain. I think the first should be changed to Aperture or perhaps removed. JeffConrad (talk) 07:44, 25 June 2011 (UTC)

Number, type, and quality of images
We’ve occasionally discussed a possible excess of images, especially ones illustrating shallow DOF. We’ve also done some housecleaning from time to time, though it’s been a pretty haphazard process. This article is now protected as a result of a silly edit war (or at least the beginning of one) over replacing one image of a cat with another. I don’t think we really need two images of a cat, and it’s not obvious that the proposed replacement is superior to the existing image.

I hope we never imply that a new image cannot be added, or that an existing image cannot be replaced with one that better illustrates a point. But we need a process for managing the image collection–a process that has at least some reasonable basis. Though it might be reasonable for an editor to propose an addition, and especially a replacement, before making the change, this approach will probably be very much the exception rather than the rule, and we have no basis for demanding it. But edit warring isn’t the solution, either, and I would think after a couple of reverts to a change or addition, it would be reasonable for the editor to discuss the issue here.

For any discussion to be productive, we need to have some criteria for what we want in images. Though I feel as if I’m stating the obvious, it seems to me that
 * Any image should serve to illustrate a point in this article, and we should probably have no more images than necessary to illustrate any given point—Wikipedia is not an image repository. In some cases, we may have more images of one type than are needed, but we may also be missing images that would improve the article by illustrating a concept that may not be completely clear from the text alone.
 * The better an image illustrates a point, the more it should be a candidate to replace an existing image or supplement what we have.
 * All else being equal, of course, a good image should be preferable to an inferior one. But I would think there should normally be a certain threshold of improvement to justify replacement of an existing image. We have several very high quality images, including that of the Nikkor lens and the Tachinid fly; I think we also have a few that are less good.

We should also have a process for objecting to an addition or replacement with which we disagree. One approach is to mention the objective here before doing anything else, but that seems overly restrictive. I would think that, at the very least, a revert would offer a brief reason why the change or replacement was not thought helpful, with a request to discuss the proposed change here. In some cases, making comment here as well as in the edit summary may be a good idea. But as obvious as this may seem, the comments in the recent mini-war weren’t very descriptive.

Perhaps it would help if we created a simple road map of images that we think we should have, and compare that with what we do have, to arrive at additional images we want, current images for which we might want a better replacement, and perhaps some current images that really don’t further this article’s purpose. JeffConrad (talk) 08:38, 25 June 2011 (UTC)

I am not sure how clued up you are with photography, but the one of the boy is an awful photo, as stated previously (I will do the same here) it is poorly lit, of poor quality, and has no points of reference, something which the cat picture does, it is also the only picture to do so. Personally, I find the other picture hurts my eyes, it is far too harsh. I am also cheesed off I was followed by the Gang of 4, who undid a load of my edits. Jamesington (talk) 10:33, 25 June 2011 (UTC)jamesington

 * If you look at my previous edits here, I think you’ll see that I understand photography, and DOF in particular, quite well. I agree that the photo of the boy is unlikely to win Photo of the Year. But it does illustrate one point quite well—that out-of-focus highlights have the shape of the lens aperture stop, and that alone may justify its inclusion until we find a better image to illustrate this point. The caption should probably be updated to reflect what I just said.
 * I assume that by “cat picture”, you mean the one you added; it’s less clear what you mean by “other picture” (the current cat picture?). In any event, I’m not sure that a “point of reference” is essential, and that a picture “hurts your eyes” is hardly justification for replacing it.
 * A confrontational approach (e.g., references to the “Gang of 4”) usually isn’t the most effective one. I agree with Ron Ritzman’s comment at AN/I: after a couple of reverts, you should have gone to the Talk pages, and those who reverted you should have provided better and less-confrontational edit summaries. I can’t exactly cast the first stone, because I’ve occasionally been a bit short with people in edit summaries, and I restored one of your edits that I would have supported reverting had I paid closer attention to the history. So to some extent, we’re all guilty as charged.
 * Getting back to the task at hand: as I’ve indicated, I prefer the existing cat image to yours (and would keep the image of the boy for other reasons, at least for now). But if replacement finds consensus, that is how it should be.
 * I suggested developing a list of desired image types so that deciding which images to add, keep, or replace might seem a bit less capricious. It might also eventually lead to making this article better.
 * Incidentally, there’s no need to add your name in signing a post—the four tildes include it automatically. JeffConrad (talk) 23:47, 25 June 2011 (UTC)

No one has made any suggestions, so I offer a few.

Current images
 * Move the image of the camera and butterfly back to the lead where it started out, because it’s most effective as an simple, informal illustration of the concept.
 * Move the image of the boy to the section Acceptable sharpness, and change the caption on to mention the out-of-focus highlights in the shape of the aperture. If a better image showing this can be found, replace this image.
 * Consider removing the two digitally processed images from the lead. It’s not clear how they relate to this article; consequently, they seem gratuitous, especially the second one.
 * Consider replacing the four images in the section Effect of lens aperture with ones in which the effect is more obvious at the size displayed. Two images might suffice, and would better match the figure at the right; the images of the jonquil flower would fill the bill quite well, they also well illustrate isolation of the background, and I'm not sure we want to include them twice.  Going to two images rather than four might oversimplify, but the effects of aperture would be more readily apparent.
 * Revise the caption for the image of the circuit board to note the softening in the plane of focus at f/32.

New image  Four images of a scene from the same camera position but with different focus settings: – One at the nearest object to be sharp, with a large aperture – One at the farthest object to be sharp, with the same aperture – One at the harmonic mean, with the same aperture – One at the harmonic mean, with an aperture that has the DOF extend from the near object to the far object I’m not sure where this would go (perhaps the lead), and some additional text might be needed to explain it. The purpose would be to illustrate what’s going on for a reader unfamiliar with photography. We’re currently loaded for bear on some of the more complex aspects, but may fall a bit short on the simpler ones (as do many other treatments). The current macro image could serve as a contrast showing a small DOF.  Images to possibly replace the four in the section Effect of lens aperture, discussed above. Better quality image to replace the one of the boy but still show the aperture shape in the OOF highlights.  JeffConrad (talk) 02:42, 28 June 2011 (UTC)

 * Jeff, I think those are all great suggestions, but I'd like to keep one CG image, like Glass ochem dof2.png, to show that the effect of DOF can be simulated by ray tracing. And I found a better cat image from the Cat article. It works both at thumbnail size and zoomed in. Dicklyon (talk) 14:37, 28 June 2011 (UTC)
 * All but the new images (arguably the most important, unfortunately) are easily done, subject to having things lay out reasonably. Unless someone objects, I’ll give it a shot.
 * I see the two cat images as about equal, though I don’t have strong feelings about them. I’ve put the other one here for easy comparison. Given the recent fracas, I think we should give others a chance to weigh in. JeffConrad (talk) 19:19, 28 June 2011 (UTC)

 * Easy part done—see how it looks. I’ve left the cat image alone for now. JeffConrad (talk) 22:12, 28 June 2011 (UTC)

 * I think File:Kittyplya03042006.JPG is the better cat picture because it has an out-of-focus foreground (the paw) illustrating DOF better. cmɢʟee☺τaʟκ 17:27, 29 June 2011 (UTC)
 * I had the same reaction, though as I’ve said, I don’t have strong feelings about the choice. If we decide to keep this image, perhaps we should revise the caption accordingly (we already describe isolation from the background in the images of the jonquil flower). JeffConrad (talk) 00:53, 30 June 2011 (UTC)
 * Yes, that one's OK, too. We could mention that the paw is closer than the near edge of the DOF and the body is farther than the far edge.  And that the DOF depends on how big you make the picture.  Dicklyon (talk) 03:59, 30 June 2011 (UTC)

cat
If you have seen my name before you know why I am here... The picture of the boy I have replaced with a cat, as it has been edited in photoshop. as it is chopped I dont think it should be highlighting depth of field when it could be an entirley fake image and some guy is just puhing his kid, just like people claim I am doing with the cat. Wikipedia is something anyone can edit right? So then instead of reverting my edits and suggesting similar pics of what I have already added why not just let me edit for gods sake. — Preceding unsigned comment added by Jamesington (talk • contribs) 23:14, 28 July 2011 (UTC)

 * Could be, but so what? Is there any reason to dislike or suspect the image of the boy?  I think it's good; and I don't see anyone pushing it who is relating to it, do you?  Chokity, who took it, placed it about a year ago, and nobody objected to it, so no pushing was needed to get it to stay.  What image hasn't been adjusted in Photoshop or some such?  A reason to not just let you edit is that you seem to have a WP:COI in really wanting your own cat's photo to appear in various articles, when other editors think it's not the best choice.  Why not just contribute where no such appearance of COI is possible?  Dicklyon (talk) 01:25, 29 July 2011 (UTC)

 * Be assured that Dick and I have nothing against your cat (or perhaps just your cat picture)—as we seem to have agreed above, the primary objective of images here is to illustrate what we discuss in the article—it’s not an image gallery. The photo of the boy well illustrates a concept in the article—that blur spots have roughly the shape of the aperture stop. This information has now been lost for the moment as a result of the games here. JeffConrad (talk) 08:52, 29 July 2011 (UTC)

 * My point is it is a horrible image. The background is harshly blotted. And the face is in a harsh light. It is not a nice picture. also shows some ambiguous hedges, as opposed to the cats obvious shoe. — Preceding unsigned comment added by 90.206.178.99 (talk) 22:51, 29 July 2011 (UTC)

 * Your point is taken. But your judgement is biased.  If someone is to decide that your photo is better, that someone shouldn't be you.  I think the image of the boy is good, and effective. Dicklyon (talk) 23:01, 29 July 2011 (UTC)

 * I can't believe we are still debating which picture(s) to include. Trying to be as neutral as possible, the boy image illustrates bokeh better while the cat image has better light. But why a shoe?

 * Why don't we instead list the phenomena we want to illustrate (e.g. bokeh and out-of-focus foreground *and* background), then someone go out and take a photo fitting the criteria, instead of picking some random photo satisfying just some of them. (Also preferably use a neutral subject to avoid allegations of pushing one's cat or kid!) cmɢʟee☺τaʟκ 01:12, 30 July 2011 (UTC)
 * The boy picture is used for one thing; its caption reads "Out-of-focus highlights have the shape of the lens aperture." It's possible someone could find or make a better image for this concept, but this one is OK.  Dicklyon (talk) 01:20, 30 July 2011 (UTC)

 * I actually have listed, in great detail, what might be good to see in images, and this seemed to find general agreement. If there are other ideas, by all means mention them. I don’t think the image of the boy is great, and honestly questioned its addition. But it well illustrates one of the points on which we seemed to agree, and I finally changed the caption to reflect the value that the image provides here. I don’t think Jamesington’s image is all that good, either—the cat’s face seems pretty dark to me (and the white patch on the cat’s throat distracts. The composition isn’t all that good, either—with the shoe at the left and the cat almost centered, the balance is off. So I think the current cat picture is better; if it were a tie, it would prevail anyway in the interest of article stability. And the picture of the boy is preferable to Jamesington’s cat picture for reasons already stated.
 * I suppose a “neutral” image couldn’t hurt, but if we were to insist on it, if might be tough to find many candidates. Because the problem here seems to be with one editor, I’m not sure we need to be too concerned. All other things being equal avoiding pictures of family members or pets is probably preferable—but I don’t think it should dictate.
 * Finally, Jamesington—would you please sign your posts with four tildes? JeffConrad (talk) 06:13, 30 July 2011 (UTC)

Near:far -- telecentric case?
At the risk of adding complexity to a long and nuanced article, this line caught my attention: "The DOF beyond the subject is always greater than the DOF in front of the subject." While that is certainly usually true, isn't it not the case for an object-telecentric system? My sense is that the typical near:far asymmetry is due to the combination of both NA and magnification decreasing with distance. For a telecentric system, I'm thinking: (1) the entrance pupil is at infinity so the angle subtended by the EP doesn't depend on distance, and (2) the magnification is uniform with distance.

On graph paper, this looks right. I have a nominal point at x=−2, a paraxial converging lens at x=0, a 2-unit-diameter stop at x=2, and an image plane at x=4. If that's correct, then the near:far distinction breaks down for a telecentric lens, No? —Ben FrantzDale (talk) 14:36, 11 August 2011 (UTC)
 * If I put another point at x=−1, its marginal rays are parallel to those of the first point (by the fact that the EP is at infinity), so the marginal rays go up to y=1 and then are columnated, making an image spot with diameter 2.
 * If I put a third point at x=−3, its marginal rays are again parallel, hitting the lens at y=3, kissing the stop at (2,1), coming into focus at x=3, and hitting the image plane at y=−1, again making a spot with diameter 2.

Depths of field plot
The plot is confusing (well, to me, anyway) and needs at least a clearer explanation, and part of the caption reads "the depth of field is increased by using a shorter focal length or smaller aperture." Shouldn't it be *longer* focal length or smaller aperture? Sergivs-en (talk) 09:02, 14 December 2011 (UTC)

Same focal length for both formats
in this section you can find following statement (take a closer look regarding info about perspective):

... the DOF ratio is the same as that given above, but the images differ because of the different perspectives and angles of view....

a few lines below one can find something different regarding the very same perspective:

... so the DOF ratio is in direct proportion to the format size. The perspective is the same for both formats, but because of the different angles of view, the pictures are not the same.

in my opinion this is of course mistake. the perspective IS THE SAME. angles of view are different because of sensor sizes, but perspective is absolutely the same. we SEE different portion of the picture but from the same perspective.

my explanation: imagine two cameras sharing the same perspective (like in 3D stereoscopic rig) with 50% transparent mirror. ignore inverting the picture, color balance and image flipping which is caused by mirror. both cameras are matched to each other, so both cameras are seeing the same picture. ZERO PARALAX, SAME OPTICAL AXIS. SAME PERSPECTIVE, SAME LENS, SAME FOCAL LENGHT, SAME F STOP, SAME SENSOR SIZE. and obviously - everything is the same. ok.

NOW - we are CHANGING one of the two cameras. this new camera has SMALLER sensor size. everythig else is as before: ZERO PARALAX, SAME OPTICAL AXIS. SAME PERSPECTIVE, SAME LENS, SAME FOCAL LENGHT, SAME F STOP. what is different now? perspective? no. just the portion of the image sensor is seeing! perspective for sure is the same, because we didn't change that.

when trying to explaing this in a different way i am often using a POSTCARD as an explanation. if we see certain landscape with the, say house in the midle of this postcard (this is our camera with bigger sensor size) we cannot change PERSPECTIVE by cutting out outer part of this very postcard, so only house in the middle is now visible (smaller sensor camera). we will see just different INFORMATION on this postcard but from the very same perspective.

that's it.

thank you,

Filip kovcin (talk) 22:19, 29 December 2011 (UTC) filip kovcin, warsaw, poland

 * It's contrasting two different ways of comparing same focal length. One case has same subject distance and hence same perspective; the other different distance and perspective, but same field width at the subject distance.  Maybe you can fix it to make the cases more clear.  The current wording "Another approach..." perhaps doesn't make it clear enough that it's introducing a different situation.  Dicklyon (talk) 00:00, 30 December 2011 (UTC)

File:Glass ochem dof2.png to appear as POTD soon
Hello! This is a note to let the editors of this article know that File:Glass ochem dof2.png will be appearing as picture of the day on July 22, 2012. You can view and edit the POTD blurb at Template:POTD/2012-07-22. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page so Wikipedia doesn't look bad. :) Thanks! — howcheng  {chat} 23:02, 21 July 2012 (UTC)

The formulas for D_F and D_N are wrong.
The final step, using the found equations for V_N and V_F in the thin lens formula gives a different result than shown in the wiki page. Solved by hand and using wolfram alpha give this result:

http://www.wolframalpha.com/input/?i=1%2Fx+%3D+%281%2Ff%29+%2B+%281%2F%28%28f*v%29%2F%28f%2BN*c%29%29%29+solve+for+x

idk how wikipedia editing/math works but someone who does should fix this

80.246.200.217 (talk) 14:35, 27 November 2015 (UTC)

 * Wolframalpha uses Mathematica.   I  use equally powerful  Maple  to solve the six equations as a set,  and obtain result easily,  see rearranged section 11, and the Maple code in the Maple link. --Gisling (talk) 07:10, 20 February 2016 (UTC).

 * And one would not normally express it as IP did, with lens-to-film distance as an independent variable. It's not clear what he thinks is wrong, but his version is certainly odd.  Dicklyon (talk) 07:40, 20 February 2016 (UTC)

Changing Away from 'lens can only focus on one point' concept in Circle of Confusion
As mentioned in the change summary, a lens focuses on a plane rather than a point. It's important for an understanding of DOF to recognize that the DOF is with respect to the plane of focus rather than the sensor (film is a sensor) plane; although for the special case of a system with limited adjustments where the lens axis is always perpindicular to the sensor plane, the DOF distances can easily be converted to be with respect to the sensor plane. This conversion has been done for decades by camera and lens makers to achieve convenient and practical use of cameras that don't have lens swing or tilt capability. That this is common practice may lead many of us to stop thinking generally and tend to think in terms of these limited-capability imaging systems that have been in widespread use for over 50 years. Editors please beware of this trap. 4.7.25.146 (talk) 21:00, 4 April 2018 (UTC)

Removed misleading synonyms for DOF. With my limited resources, I couldn't find a reliable reference that equates "focus range" or "effective focus range" with DOF. It wouldn't be a big surprise if it is contained somewhere in the context of limited adjustment cameras; or in operator's instructions written with marketing or public relations in mind; however, it would add to the misconception that DOF may generally be obtained by simply measuring from the imaging system to objects imaged with acceptable clarity, and subtracting the nearest from the farthest. This will only work when the lens axis is perpendicular to the sensor plane of a flat sensor. 4.7.25.146 (talk) 19:16, 7 April 2018 (UTC)

Article is massive
Right now, the article is extremely long! Over two-thirds of the article is taken up by the sections "DOF Formulae" and "Derivation of the DOF Formulae". These seems unnecessary and possibly be split into their own articles or removed outright. Not even the physics or mathematics articles have such lengthy derivation sections. MarkH21 (talk) 10:41, 8 January 2019 (UTC)

 * Removed the formulae sections because Wikipedia is not a textbook (WP:NOTTEXTBOOK). MarkH21 (talk) 06:15, 14 January 2019 (UTC)

 * I agree it's massive and bloated, but it would probably be better to cut it by about half than to throw out all that work of many editors over many years. If you think a split to another article on DOF math is a solution, let's consider that, too.  But just chucking it all out seems like not the best solution. Dicklyon (talk) 06:23, 14 January 2019 (UTC)

 * A massive trimming or split of the formula section are possible solutions that I would probably be fine with. With regards to the derivations, I believe that it should be entirely removed. Its inclusion does not really make sense, Wikipedia is not a textbook nor is it a place to give the mathematical derivation of known scientific & engineering phenomena. Anyone who wants to learn about how to derive the formulae would just refer to the referenced textbooks / sources, as one would do for any other subject with mathematical formulae.

 * Just to note, whether editors have spent significant time writing material should not be a consideration for whether written material should be kept. That's not to say that the work isn't appreciated or potentially valuable though! MarkH21 (talk) 08:15, 14 January 2019 (UTC)

 * Following WP:NOTTEXTBOOK / WP:NOTHOWTO, I have trimmed the "DOF Formulae" section down while retaining most of the formulae, but I'm still not convinced that the section belongs. The derivations section is gone because that really does not belong.

 * There are still some overly-detailed sections and material more fitting of a textbook/how-to, so I am adding the "how-to" tag. MarkH21 (talk) 13:57, 20 January 2019 (UTC)
 * The derivations aside -there's quite a lot of repeated content in the article and it's at quite a high level. I think there is a fair amount of rewriting that could be done and I'm happy to make a start on that if people are happy to look over my shoulder a bit? Joe (talk) 17:26, 24 January 2019 (UTC)
 * I took an initial swing. Will come back with more books shortlyJoe (talk) 19:37, 24 January 2019 (UTC)
 * So far, the revisions look quite good and are much appreciated! Thanks! MarkH21 (talk) 04:43, 29 January 2019 (UTC)
 * Thank you - it makes it much easier to keep going when there's a vote of confidence. :) Joe (talk) 09:54, 29 January 2019 (UTC)

Maybe we should make an article Depth of field formulae and derivations or Depth of field calculations or something like that to preserve the bulk of the removed material? Dicklyon (talk) 05:18, 29 January 2019 (UTC)
 * I think that's a sensible suggestion and I'd be for it. My personal preference is to leave the formulas (and derivations) until the structure of the rest of the article has played itself out (because some formulas might end up inline, and I feel like some aren't relevent to DoF anyway...) but I'm without strong opinion on it. Joe (talk) 09:54, 29 January 2019 (UTC)
 * I've now looked over the derivations that were removed properly. I think we should have formula (because it provides the exactness that we can't deliver with a general introduction text), and I think that the derivations help with that; however I don't think these are particularly clear derivations even to someone with a fairly solid maths background - I think that we'd do much better with geometric deviations some text and a bunch of diagrams. I'm still on the fence, but I'm now at "I think we should probably have derivations, but I don't think those derivations are half as good as you'd find on YouTube" Joe (talk) 10:13, 29 January 2019 (UTC)
 * Please, let's place the redacted derivations into the suggested Depth of field formulae and derivations or Depth of field calculations article (or the like). There are plenty of links at photography forums such as photo.net, dpreview.com, photography.stackexchange.com, etc., that have linked to this article for years, and now (apparently) suddenly, the information is gone. sbb (talk) 01:30, 24 March 2019 (UTC) 'Edit: While the information might better belong at Wikibooks, the simple fact is that so much of Wikibooks' content is just poor. It has no life, community, or upkeep, from most of my readings there. So what was well-written, and pretty well diagrammed, is now just lost to the ether.

Todo list
Some bits I'd like to do in the future - I thought I'd put them here so a) I don't forgot and b) people have a chance to object.

 * I'd like to improve the explanation of what depth of field and circle of confusion actually *are* so it's obvious to the non-technical reader
 * I'd like to add in some diagrams (hopefully animated) and proper text for how the depth of field changes with focal length, subject distance, and aperture.
 * I'd like there to be a decent section on Bokeh, there should be some nice illustrations of things like fancy heart shaped Bokeh ( has the right licence)
 * I'd like to have some notes on the extremes of depth of field (lots of examples in
 * From the above - would be nice to add in some content on Group_f/64 for a bit of colour
 * The 'object field methods' section needs work - Merklinger's work appears to be self-published (interesting to read thought tho - and cited a few times in Google Scholar (but hardly mentioned in Google Books) - and it's been presented as the main opinion with Ansel_Adams being relegated to the 'other people think' section. :s Joe (talk) 09:57, 29 January 2019 (UTC)
 * The examples of extreme depth of field weren't actually that good, but group 64 should be excellent. I've also added the heart shaped bokeh. I've done some more rewriting today, but I'm also noticing that a lot of the content isn't about depth of field and really belongs in aperture or one of the other photography/optics articles.Joe (talk) 21:37, 27 January 2019 (UTC)

I'd keep the Bokeh stuff in its own article. I like Merklinger's work, and it's respectable enough, being cited, though self-published. Dicklyon (talk) 18:13, 29 January 2019 (UTC)
 * For sure, I mistakenly wrote bokeh above when I meant 'illustrate that points turn into the shape of the aperture by way of the cool heart shaped ones' - I do think that we should link up a little better with Bokeh as well. Joe (talk) 16:09, 30 January 2019 (UTC)

Object Field section
I'm looking at Depth_of_field and having read the main source I've got a few issues....

 * 1) The key part of the Object field method Merklinger proposed seems to be about making it easy to calculate depth of field - but that's not in the section
 * 2)  The section draws a false contrast. Adam's appears to be saying: "Photos look better when close things are as sharp or sharper than far things" (I don't have that source, but I understand that matches up with his body of work), whereas Merklinger is saying "if you want to read text on a boat that's far away, then you have to make sure it's very sharp - you don't have to work as hard if it's close." - I don't think those two views are particularly in conflict and I feel like they should be presented as such.
 * 3) It feels like it's in the wrong bit of the article - at this point the reader doens't know what influences DoP, or even that the focus point isn't in the middle - I feel like those bits go first.

I'm unsure how to rewrite (or restructure) to get this right - does anyone have any ideas (or the Adam's source)? Joe (talk) 19:20, 30 January 2019 (UTC)

 * I think the object field method is sensible as a scheme in which both Adams's and Merklinger's contradictory opinions can be illustrated and contrasted. It's also used in a neutral way by von Rohr, as described in the Thomas Dallmeyer 1899 book (and see my unpublished survey about this stuff).  There's more in Dallmeyer's book than I realized at the time (before I had Google Book Search to help me).  You can't count on my unpublished synthesis, but you might find it a useful guide to the history and approaches. Dicklyon (talk) 18:14, 31 January 2019 (UTC)

 * The closest thing I see in the cited Adams 1980 book is this bit. Dicklyon (talk) 18:31, 31 January 2019 (UTC)
 * No, it's on page 51 more explicitly:, as our ref 5 says. Dicklyon (talk) 18:42, 31 January 2019 (UTC)
 * Thank you muchly on all counts! The sources and the review a both going to be brilliant - I'm semi-learning this as I edit (I *thought* I knew about it) and it's great to have someone with real expertise looking over my shoulder :) Joe (talk) 09:55, 1 February 2019 (UTC)
 * Now I've read your PDF (abeit lightly) I've a much better idea of the structure I think we should have, and in the process I suspect it solves some of our formula problems above. Today I've added a bit of content to introduct object field to the passer by, and I've also moved it - because I think we should have an introduction to the 'standard' approach before presenting an alternative - to make this work I might see how the 'effects' section looks with a similar DoP formula using focal length.Joe (talk) 15:27, 2 February 2019 (UTC)
 * Jeff Conrad had a ton of expertise, too, but tended to be more wordy than me over the last 13 years, as you can see by how much text he added. I've mostly just tweaked things, trying to keep the errors out.  If you can come up with a cleaner and leaner article, that will be great. Dicklyon (talk) 03:58, 3 February 2019 (UTC)
 * On that topic - how would you feel about (once we've done a bit more cleaning up) putting the article forward for GA? I'm mostly thinking of it because it would be nice to have the article looked at by someone who actually isn't familiar with the topic and it's a nice thing to go for :) Joe (talk) 13:58, 3 February 2019 (UTC)
 * I've never engaged in such processes, but yes it could be useful. Dicklyon (talk) 17:17, 3 February 2019 (UTC)
 * After more cleaning up, I would also support such an endeavor! MarkH21 (talk) 22:31, 4 February 2019 (UTC)

Recent changes.
Did a couple of fairly violent changes just now - thought I'd stop to let other people check them over.

 * I added a basic depth of field formula to the top of the article because I think it helps and because otherwise we kind of ambush people at the end.
 * I folded together the overview and 'factors affecting' sections largely to see how it looked - I think it works quite well and I'm inclined to keep it.
 * I removed a couple of images (we have a lot - and we've lost a lot of wordyiness so there's some traffic) and moved others around.

Comments welcome - going to edit somewhere else for a bit. Joe (talk) 19:54, 8 February 2019 (UTC)
 * Nice! It does look better. Quick comment, do you think there's any way to cut the Table of Contents down a bit, i.e. section/subsection/subsubsections to remove? Seems like a very long TOC relative to the article length now... — MarkH21 (talk) 11:31, 10 February 2019 (UTC)
 * Thank you!  Re:TOC - it's shorter than it was a couple of minutes ago - I did a few relatively small changes recently. I think that Depth_of_field is going to get rewritten into a paragraphy, so that will reduce the TOC - I also think that some of the formula are starting to feel like they want to be in the apropreit sections - so that will reduce down quickly.  Joe (talk) 20:07, 10 February 2019 (UTC)

Contining Violence
I've been continuing my near-violent changes. I think we are nearly there thought.

The three things that I think need to be done before submitting for GA review are:

 * 1) Consistent referencing
 * 2) Sort out formula section
 * 3) Thorought proofread.

I got most of the way thought the referencing a while ago - it only needs a bit more work - particular on the difraction section that came back. I did a fair amount of work on the formula section today - getting steadily more unhappy with it as I went. I think we need to get a single consistant mainstream textbook or source and start it from scratch. At the very least we should be using the same symbols thoroughout the section. Will investigate the library and come back in a few days to see were we are.Joe (talk) 17:17, 17 February 2019 (UTC)
 * Oh yeah, rewrite the lead - the article has changed a lot so it will probably need an overhaul.Joe (talk) 17:18, 17 February 2019 (UTC)
 * It's looking good. But an awful lot was lost; did you collect it some place? Dicklyon (talk) 03:15, 24 March 2019 (UTC)

Lead, 1st caption, section title and content, POV
LEAD The lead still seems too POVish; but, now the POV is not hidden from the casual reader. Salvaggio et al clearly stated their assumption. The reference and link to "focus stacking" was removed because that article seems to have no reliable basis. Also the 'can't be done by traditional methods' comment was removed as being unsupportable.

1st CAPTION Reworded the caption

SECTION TITLE AND CONTENT Changed section title to "Overcomming DOF limitations" to more accurately reflect the intent. Made a few improvements to the wording. Left "focus stacking" in but maybe "image stacking" is a more widely used term (Adobe uses "image stacking") and there doesn't seem to be a reliable reference for "focus stacking".

POV The article is written from the POV that cameras have a lens axis perpindicular to the sensor plane; that can be very misleading. May want to consider using Conrad, Merklinger, Ray, Wheeler, and others that show what DOF is more generally. The general still applies to the current POV.

208.54.86.201 (talk) 02:00, 8 June 2019 (UTC)

Blurry hearts picture
The blurry hearts illustration has more to do with the fact that aperture shape affects the shape of blurry spots; but within the DoF, the blurriness is not noticeable. This is looking like a "how-to" photography-art guide. Seems appropriate for an article that discusses aperture shape and artistic blur; which, might not belong in WP (textbook stuff?). - NewageEd (talk) 10:24, 23 January 2020 (UTC)

Estimate dof in image dimension
This is a new logic I have been working on, no publication so far but I will appreciate if somebody is interested in writing an article on this topic. Feel free to contact me, thanks.

he key point is that when we work in the image dimension instead of the scene the equations become very simple. The size of the focus blur varies linearily along a plane in the image

The relation is;

$$s = \frac{a}{h} \times d$$ where:

 * a is the numerical aperture
 * h is the "altitude" above the plane. This value can be adjusted if the camera is tilted with the cosine of the angle with the plane.
 * d is the distance of the point from an origin in the focus plane (where s=0)

The demonstration is here

A first conclusion is that the focus is at exactly at the middle distance between the near and far dof limit. Again this is true in the image and along a plane.

Then we have a relation to set the f# for having everything in focus between the focus plane and the near/far limit

$$f_\# = f \times \frac{k}{h} \times r$$
 * f is the focal length, h the altitude.
 * k is a constant representing the minimum resolution, k =800 is consistent with the results given with common circle of confusions with classic dof calculators
 * r is the ratio of the image height between the focus and the near or far limit (for instance 1/3 of the height).

There is also a relation taking into account diffraction:

$$n = 134 \sqrt{\frac{rf}{h}}$$ The links are here:

 * The theory
 * DOF calculator]
 * A video on youtube to use the calculator — Preceding unsigned comment added by Chrisinparis (talk • contribs) 16:48, 28 January 2024 (UTC)
 * Do not hesitate to give me your feedback, I want to do it the clean way. The equations are disclosed, it is quite simple in fact,it simply uses a different logic Everything is explained in the links. Feel free to contact me !! Chrisinparis (talk) 18:58, 30 January 2024 (UTC)

title: Talk:Depth of field


text:
Talk:DNA/Archive 1

OK, time to fuss about nomenclature here.

nucleosides are glycosides of bases, whereas nucleotides are the phosphate esters of nucleosides.

The names for each kind of molecule containing the same type of base are different, ie adenine vs adenosine vs adenosine monophosphate.
 * adenine is the base
 * adenosine is the nucleoside
 * adenosine monophosphate is the nucleotide

I'm not sure where this goes, but it should go in one of the biochemistry-related articles, and it should be borne in mind when writing and editing these articles.

(I have trouble keeping the nomenclature straight myself, having picked up most of my biochemistry along the way, rather than formally. So, this is why I'm maybe a little cranky on the issue ;-)  --dja The bases are adenine, guanine, thymine, cytosine, uracil.

The nucleosides are adenosine, guanosine, thymidine, cytidine, and uridine.

- I think I made a decent page describing sticky ends and blunt ends and I would like to connect to it from the DNA page. I think it might be good to have a page addressing DNA manipulation techniques, but that is a rather cumbersome name for an article. Can anybody suggest a better name? Recombinant DNA technology? DNA manipulation? Thanks adam -- In the DNA page and in the hydrogen bond page emphasis should be given to the fact that the main force responsible for the double helix stability in water is definitively NOT the hydrogen bond! This is a common misunderstanding even in the biochemistry community. Hydrogen bonds are fairly weak in a water environment becuase they readily break up forming new bonds with water molecules. Hydrogen bonds are responsible for the BASE PAIRING. The stability of the base pair and the double-helix shape are instead prevalently determined by hydrophobic effect in the stacking of the base pairs. See "Understanding DNA" by Calladine for review. -- -- Answer: The H bond between two organic molecules is a (kinetically?) *weak* bond in a water solution,because water molecules will try to bind more strongly by H bond itself than almost any other molecule. This does not mean it is not important. It is true that base pair in specific ways (WC, Hoogsteen etc.) by mean of hydrogen bonds. Specificity is given by H bonds,indeed. Therefore,when two DNA strands meet in water, it's the high number of complementary H bonds that starts the annealing,probably. If an unsufficient or a geometrically unstable number of H bonds form, no annealing starts. But what makes them remain annealed is mainly (not only,but mainly) hydrophobic effect, as far as I know. The double helix allows the bases to be rigidly stacked, probably lowering entropy cost. Moreover, the helix curve of the phosphate backbone hides the bases from water, better than a single strand would do. At least,that's what I studied in an advanced DNA biochemistry course about 18 months ago...I'll go back to the books and I'll see if I'm right,or it's just my memory falling out.
 * But you could have base stacking in a single helix, so it's hard to see how it could be just the energetic payoff from stacking that glues two strands together. 168...

-
 * So, you seem to be saying that the complementary base-pairing just provides a pathway to a conformation that derives its stability primarily from stacking and from a stearic exclusion of water that creates a high activation energy barrier to de-annealing. But if we are really talking about an equilibrium stability of the double helix and not a kinetically trapped metastable state, I think we can disregard the activation energy barrier posed by the protection of the H-bonds by the backbone. I think the way to think about this is that the bases of two complementary strands could H-bond to water, and yet they choose to bind to another base in the complementary strand. The bases of a free strand could stack without pairing, but perhaps entropy considerations for a strand in solution (where no complementary strands are present) favor a disordered conformation, in which the energy rebate to be derived from stacking goes unexploited. The presense of a complementary strand provides bases an H-bond opportunity other than water, which I suppose changes the entropy considerations and costs, and allows the strands to cash in on the stacking rebate.

 * But to what do we credit the annealing of the strands? I wonder if giving credit to the stacking represents a focus on enthalpy and not on entropy. It seems to me that the opportunity for complementary base-pairing merits a lot of credit, because it somehow changes the rules of the entropy game significantly. Otherwise, two complementary strands would do exactly what two non-complementary strands do in solution, and float around as disordered chains. 168... 23:54 5 Jul 2003 (UTC)

- Hello! I'm the stacking-flamer guy with confused ideas :)! Ok,I went on books a minute (Calladine-Drew "Understanding DNA" and W.Saenger "Principles of Nucleic Acid Structure"). I dont' have them with me now,but here's what I remember now...

Saenger book confirmed me that H bonds between bases are actually *weak* in an aqueous environment

 * But you said that the H-bonds between paired bases are shielded from the surrounding water (168)

and can't provide energy for the double helix stability. It talks about DNA annealing almost as 168... says above : "...the complementary base-pairing just provides a pathway to a conformation that derives its stability primarily from stacking and from a stearic exclusion of water that creates a high activation energy barrier to de-annealing."

That's the sense I grasped from the book.

"I think the way to think about this is that the bases of two complementary strands could H-bond to water, and yet they choose to bind to another base in the complementary strand." This seems not to be the (main) case...

 * What do you mean by "this"? How could it not be the case in DH DNA? (168)

"The bases of a free strand could stack without pairing, but perhaps entropy considerations for a strand in solution (where no complementary strands are present) favor a disordered conformation, in which the energy rebate to be derived from stacking goes unexploited."

In truth, both books tell me that single stranded DNA/RNA actually stack their bases! Moreover,it seems there are addictional interactions between sequential bases that help stacking.

Bases of a free strand stack,but they pay an entropic cost to do it

 * If the base-pairing H bonds hardly count enthalpically and if the bases stack in both ss and DH DNA, then one has to conclude that the only thing that makes DH DNA more stable than ssDNA is an entropy effect due to H bonds, and hence H bonds are more important than stacking. Where's the mistake here? (168)

(and,in fact,that stacking should be quite loose). The DH structure instead provides a sterically relaxed but rigid framework for base stacking, with additional protection from the watery environment. Correct geometry and initial pairing is due to bases H-bonds (and that's emphasized). But the dG stability derives from the stacking,it seems again... ?

 * dG stability? I don't know what you are referring to. (168)

I think it's right we're talking of a mostly enthalpic contribution!

Well,I always write these at night and I'm very tired...hope to fix soon some of what I've said.

 * Well, thanks for thinking about it. I'll be interested if we can get to the bottom of it. 168... 01:57 11 Jul 2003 (UTC)

- Here's all the article says now about the H-bonds' role in double-helical structure:

"In a DNA double helix, two polynucleotide strands come together through complementary pairing of the bases, which occurs by hydrogen bonding....Because pairing causes the nucleotide bases to face the helical axis, the sugar and phosphate groups of the nucleotides run along the outside..."

I don't believe anything anybody has asserted above implies that this is wrong or misleading. That doesn't mean that there isn't anything worthwhile to add to the article regarding stacking. I can think of one place to put it: Right now the pitch (~10 bp per helical turn) is mentioned but unexplained. So I suppose a phrase invoking base stacking might be inserted in that context as a bit of explanation, which would at the same time point to how strongly a role it plays in the double helix. 168...

Actually, I just went in and inserted something like that. 168... 00:21 6 Jul 2003 (UTC)

The historical account of the discovery of the structure of DNA given in this article appears to contradict Watson's The Double Helix. In that account, Watson and Crick's failed model (with the backbone inside), predated their knowledge of the B-form discovered by Rosalind Franklin. Even when they had secured access to the B-form diffraction photograph, they still exhaustively explored backbone inside models before experimenting with backbone outside ones. This discrepancy needs resolving. -- Alan Peakall 15:08 Jan 6, 2003 (UTC)

Hmmm. Sounds perfectly plausible, if not familiar. In telling/editing the history, I have been following the lead set by a previous contributor to this page, and I don't have the Double Helix/8th Day of Creation/etc on my bookshelf. Can anybody propose a narration of what Franklin's presented and what model W&C went home to build in response? If Franklin did perceive that the phosphates are outside, was it on the basis of the data that she showed at the alleged presentation that this article cites, did she present this implication of her data explicitly, and if she did, why would W&C have dismissed or forgotten this finding when they went home to build a model that would agree with her data? Perhaps the point of the original author of this history was to credit Franklin with being the first to realize the phosphates were outside, but he or she didn't know exactly how to put it, or put it so vaguely that under editing the text wandered from the truth.168... 20:09 4 Jun 2003 (UTC)

-- [User:MikeS] Very interesting, thanks. I do have a question, I hope has an answer.

First, some have written about "genetic diseases" perhaps based on DNA strand segments being identical between parent and offspring, in "functionally-similar" locations along the DNA, with the child having, or being "pre-disposed" to, the illness of the parent. I understand there is an island off Venezuela in which all suffer from the same eye disease and the common DNA segment has been identified but, no cure was known, (c. 1998?).

Second, the fight against the West Nile Fever now depends on the fact that the DNA of infected chickens is altered when they are infected, even though they show no syptoms of the disease.

So, which is true? Is the gene altered by the disease or is the disease the consequence of a DNA "genetic disease" gene strand segment. Seems like a chicken-egg question, but it is, most definitely, not. Could the people in the island be infected by the same virus and their DNA show the same evidence as the West Nile Fever infected chickens? Health Insurance companies and buyers are placing their bet on the answer. 24-Jul-03[User:MikeS] -

I'm a little confused by your question and don't know the island or disease you're talking about (there's Oliver Sack's book "The Island of the Color Blind," but that island in question isn't off Venezula, I don't think). But I think I might be able to help a little. There was a Nobel Prize awarded to the people who discovered that cancer may come either from the DNA in our chromosomes or from viruses. On the one hand, a virus may carry around defective copy of an oncogene, so that an infected cell makes a cancer-causing protein in reproducing the virus. On the other hand, the chromosomal oncogene in one of a person's cells may go defective by itself, through mutation. So here's a case of a disease that can be one or the other. Another thing about certain types of viruses is that they insert their own DNA into the chromosomes of their host cells. The insertion can disrupt host genes at the sites of insertion. 168... 18:18 24 Jul 2003 (UTC)

-- [User:MikeS]The answer is clear. It could be either and if we focus on the molecular biology, much research work will lead to a new highly profitable drug. If the focus is to find the mosquito, or whatever caused the infection, well, you know. However, to be explicit. If we agree, and the evidence shows, that some illnesses alter DNA; and, as evidence also shows, the DNA has a marker that identify those that were infected, Then, like the previous pointed out, there is no way to know if the DNA segment was caused by an illness or inherited. In either case, Insurance companies may save money by DNA examination. Therefore, it should be illegal?

To be more explicit. If the focus is on "curing" by DNA modification, and this has been tried with promising and deadly results, then it appears to ignore immediate causes, you know? Like larvae in drinking water, mosquito bites, pollutants and pollen in the air, etc. That is, we will ignore the cause and deal with symptoms. Sounds familiar? --[User:MikeS] --

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:DNA/Archive 1


text:
Declaration of independence

A declaration of independence, declaration of statehood or proclamation of independence is an assertion by a polity in a defined territory that it is independent and constitutes a state. Such places are usually declared from part or all of the territory of another state or failed state, or are breakaway territories from within the larger state. In 2010, the UN's International Court of Justice ruled in an advisory opinion in Kosovo that "International law contains no prohibition on declarations of independence", though the state from which the territory wishes to secede may regard the declaration as rebellion, which may lead to a war of independence or a constitutional settlement to resolve the crisis.

title: Declaration of independence