Talk:Depth of field

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

text: 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)
thread_title:  DOF - Increases vs Decreases 

message: 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.,  should be ).
* I doubt that it’s obvious to most readers that the near limit of DoF for infinity focus is  (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#Mathematical phenomenon using the same symbol H. The phenomenon holds only for the approximate hyperfocal distance
::H \approx \frac {f^2} {NC}\,.
* 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  rather than ). 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.
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.
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)
thread_title:  Hyperfocal distance depth of field using EasyTimeline 

message: 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 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.
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)
thread_title:  Near:far -- telecentric case? 

message: 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)
thread_title:  Depths of field plot 

message: 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)
replies: text: 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)
thread_title:  Same focal length for both formats 

message: 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)
thread_title:  [[:File:Glass ochem dof2.png]] to appear as POTD soon 

message: 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)
replies: text: 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)
replies: text: 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)
thread_title:  The formulas for D_F and D_N are wrong.  

message: 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)
thread_title:  Changing Away from 'lens can only focus on one point' concept in Circle of Confusion 

message: 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)
replies: text: 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)

text: 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)
thread_title:  Todo list 

message: I'm looking at Depth_of_field#Object_field_methods and having read the main source I've got a few issues....
# 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
#  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. 
# 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)
replies: text: 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)

text: The closest thing I see in the cited Adams 1980 book is this bit.  Dicklyon (talk) 18:31, 31 January 2019 (UTC)

text: No, it's on page 51 more explicitly: , as our ref 5 says. Dicklyon (talk) 18:42, 31 January 2019 (UTC)
replies: text: 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)
replies: text: 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)
replies: text: 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)
replies: text:  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)
replies: text: I've never engaged in such processes, but yes it could be useful.  Dicklyon (talk) 17:17, 3 February 2019 (UTC)
replies: text: After more cleaning up, I would also support such an endeavor! MarkH21 (talk) 22:31, 4 February 2019 (UTC)
thread_title:  Object Field section 

message: 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)
replies: text: 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)
replies: text:  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#Other_applications 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)
thread_title:  Recent changes.  

message: 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: 
# Consistent referencing 
# Sort out formula section 
# 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)
replies: text: 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)
replies: text: It's looking good.  But an awful lot was lost; did you collect it some place? Dicklyon (talk) 03:15, 24 March 2019 (UTC)
thread_title:  Contining Violence 

message: 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)
thread_title:  Lead, 1st caption, section title and content, POV 

message: 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)
thread_title:  Blurry hearts picture 

message: 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)
replies: text:  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)
thread_title:  Estimate dof in image dimension