Auto Depth of field

[al_hughes]

In my eos film cameras I could ensure everything was in focus by aiming focus pont in front and back of subject to ensure all in focus.

I cannot find it on my Canon 6D.

Suggestions please..

[JosvanEekelen]

<p>Good question. I rarely used it on my EOS 5 and EOS 30. Just checked, EOS 10D still has the A-DEP feature but it is already missing on the 5D (original). Canon must have dropped the feature long ago and since I've never seen questions for it before I don't think it is widely missed. Perhaps we can start a petition: give us back ECF and DOF control (and Kodachrome) :-)</p>

[david_henderson]

<p>Use Live view and magnified focus. Its better. </p>

[al_hughes]

<p>Thanks for suggestions. Will try live view and also f22 !</p>

<p>Thanks.</p>

[Marcus Ian]

<p>It may be better, but it sure ain't faster!</p>

<p>as far as f22 goes, I wouldn't want to have try to check focus @ f22 ! </p>

<p>I think the reason they did away with it was the simple thought that any scene static enough to use A-dep (or, LV & mag focus) would also be static enough to take an exposure, check, then adjust. Not an ideal workaround IMO, but frankly, probably realistic in the vast majority of cases. </p>

 

[JDMvW]

<p>Although the markings for DoF, etc. are mostly long gone on AF cameras and lenses, a careful reading of articles on "hyperfocal distance" (starting at http://en.wikipedia.org/wiki/Hyperfocal_distance ) will yield useful information that can be used in manual settings on the camera.</p>

<p>Otherwise, as said, use a small aperture on aperture-preferred and watch your shutter speed. However, going down to f/16 or f/22 can cause loss of sharpness from diffraction ( http://en.wikipedia.org/wiki/Depth_of_field#Diffraction_and_DOF ). As Ms. Hepburn said, "You can't have it all".</p>

[bobatkins]

<p>The old EOS "automatic depth of field" mode is explained in some detail here - http://www.bobatkins.com/photography/eosfaq/eosfaq24/9miscellany.html#q27</p>

<p>Ir wasn't perfect, but it was faster than trying to calculate things yourself. With the 6D (or any other EOS DSLR) there is no "DEP" mode. Not sure why but I suspect Canon found that it wasn't very accurate (at least the way it was done "back in the day"). There's no reason it couldn't be done with current DSLRs other than perhaps it might confuse more users than it helped. However given the number of bells and whistles found in most DSLRs these days, one more couldn't really hurt.</p>

<p>I have a long and slightly technical discussion of DOF, along with a DOF calculator here - http://www.bobatkins.com/photography/technical/depth_of_field.html</p>

<p>There are a bunch of smartphone iOS and Android apps for DOF calculation if you want do do calculations in the field. For example http://play.google.com/store/apps/details?id=com.aimenrg.dof&hl=en</p>

<p> </p>

[ted_marcus1]

<p>The DEP feature on the EOS 650 (the very first EOS, released in 1987) was one of the things that convinced me to go with Canon rather than Nikon back in 1989. Although it wasn't perfect, I found DEP extremely helpful in many situations. The Elan II that replaced the 650 in 1998 had the same DEP feature.</p>

<p>When I went digital with a Rebel XT/350D in 2005, I was disappointed to find that DEP has been replaced with A-DEP. Although it was presumably supposed to be easier to use than the "legacy" DEP, I found it not only less useful but less accurate. I couldn't understand why they had to replace DEP with A-DEP, but I assumed that the reason had more to do with marketing than technology.</p>

<p>Last year I replaced the Rebel XT/350D with an SL1. The SL1 lacks any automatic depth of field feature. I do take advantage of the ability to check focus manually by magnifying the view on the LCD, but that takes a lot more time, effort, and squinting. It's not convenient at all. Given the available processing power and the low cost of ROM, I'm again convinced that the decision to eliminate DEP/A-DEP was made by marketeers, for reasons known only to themselves. I'd guess they decided the target market would be better served by devoting the available resources for gimmicky "scene" modes and direct sharing to social media.</p>

[bobatkins]

<p>You're probably right Ted. I think today's average DSLR user is much more familiar with WiFi connection and image sharing than with the concept of depth of field. Of course there's no reason you couldn't have both.</p>

<p>The cynic in me considers the possibility that DEP modes were removed so that some time in the future they could be added back as a new selling feature in a subsequent DSLR upgrade...</p>

<p>There are Canon firmware hacks like Magic Lantern and DHCK, which add some missing features, but as far as I know neither of them includes any type of DEP or A-DEP modes.</p>

[jeff_conrad]

<p>My sentiments are about the same as Ted’s—DEP (the real one) was one of the reasons I switched to Canon in the early 1990s. As Marcus notes, whatever Live View may offer, it’s far slower than DEP. And I’m not sure it’s any more accurate—unless you have all day to set focus and <em>f</em>-number.</p>

<p>I never understood the alleged “7/17” focus distance (and it was never stated whether this was the object distance or the image distance). So I decided to do a few tests with an EOS-1v and an EOS-5, and determined that DEP did no such thing. Rather, it appeared to set something very close to the harmonic mean of the near and far distances, probably setting focus to the middle of the image distances—just as was done with DoF scales on manual-focus lenses. In short, the focus set by DEP was as good as I ever could do with DoF and distance scales, and it took a fraction of the time. The <em>f</em>-number was supposedly determined using a circle of confusion of 0.035 mm, but I found this a bit optimistic, and preferred to close down about a step whenever possible. The 0.035 mm criterion was a bit loose—purportedly based on enlargement to 5x7—so I’d often go down one additional step. The nice thing, though, is that the optimal focus distance is independent of the <em>f</em>-number, so the process was simple and fast. It was especially easy on the EOS-5, working much like program shift. The EOS-1v took a bit more work, changing to manual mode after letting DEP set the focus and <em>f</em>-number.</p>

<p>The theory behind this isn’t rocket science, and it’s essentially what was done for years with large-format DoF calculators and DoF scales on manual-focus small-camera lenses. I discuss it in detail at <a href="http://www.largeformatphotography.info/articles/DoFinDepth.pdf">http://www.largeformatphotography.info/articles/DoFinDepth.pdf</a> (skip to Focus and Minimum <em>f</em>-Number for Given Depth of Field if you just want this topic).</p>

<p>I discussed the elimination of this feature extensively with Canon USA, and they told me they were never given a reason, though they guessed—probably correctly—that few people used DEP. As Bob hints, you usually don’t care about DoF in a selfie. Most people don’t know much about DoF, and really never did. But elimination of DEP was a loss for the few who did understand it, and needed to optimize DoF in their images. Today’s multi-thousand-dollar DSLR’s cannot do what I could easily accomplish with a Pentax K-1000. Somethin’ ain’t right here ...</p>

<p>I’m always amazed by people who extol the virtues of DoF calculators. No question, they give you the answers, but then how do you set the camera using a microscopic distance scale? And most of the calculators don’t address the simple question of “What focus and <em>f</em>-number do I use to get everything sharp between point A and point B?” And of course the camera’s AF is nonfunctional with this approach. DEP handled this well and did it fast.</p>

<p>Conceivably, you could do the job using a laser rangefinder to measure the object distances, and then use a calculator. The <em>f</em>-number could then easily be set, but what about the distance? I guess you could scan the scene with the rangefinder until you found an object at the calculated distance, and then focus on that distance using the camera’s AF. Again, somethin’ ain’t right here ...</p>

[bobatkins]

<p>Well the "7/17" comes from Chuck Westfall of Canon, who is the guru of all things technical to do with the EOS camera line. I presume 7/17 was the ration of (near focus to subject)/(distance from subject to far focus). There is always a great DOF behind the focus point than in front of it (though it approaches 1:1 as you get closer and closer in the macro regime). There's a 1/3:2/3 DOF "rule" which is sometimes applied but that's just an easy set of numbers to remember rather than a number based on any specific situation. 7/17 would have been precisely correct in some situations and an approximation in others. It's probably good for whatever distances Canon thought were most likely in typical use (i.e. not macro and not with the far point at infinity).</p>

[jeff_conrad]

<p>Bob, I have the utmost respect for Chuck Westfall. But I still don’t buy his “7/17” assertion, for several reasons.</p>

<ol>

<li>Again, it wasn’t stated whether this ratio applied to the object or image side of the lens. I’d probably assume the former (as you seem to do).</li>

<li>A “7/17” ratio would make no sense on either the image side or the object side, except at one distance.</li>

<li>Though I certainly don’t know the details of Canon’s AF system, implementing a “7/17” ratio would seem difficult on either the image side or the object side. The machinations of adjusting the image distance to achieve a “7/17” ratio on the object side are pretty involved—work the math if you don’t believe me.</li>

<li>I tend to believe what I observe more than what I hear. I consistently got the same results from two different cameras introduced about eight years apart, and with several different lenses, both zoom and prime; about half were L’s. I don’t suggest that I was able to determine focusing distances to the nearest millimeter, but the tests were nonetheless designed so that I could not possibly have mistaken a “7/17” ratio for an approximate harmonic mean distance. And I repeated the tests a few months later and got essentially the same results.</li>

</ol>

<p>I got the distinct impression from Canon that DEP was gone and never coming back, so we’ll probably never get a definitive answer. But I measured what I measured, and what I measured makes a lot more sense than the “7/17” ratio.</p>

<p>Another way to look at it: DEP actually worked much better than the “7/17” ratio would suggest.</p>

<p>Getting back to Al’s original question: as ridiculous as my suggestion of using a rangefinder and calculator may seem, it’s about all I can suggest other than to just wing it. I used to think that DoF discussions that concentrated on the object side were misplaced, but I guess AF—and the demise of DEP—make them relevant once again.</p>