DPAF's Underlying Tech the Villain? (When all else ruled out)

[YuengLinger]

[Since starting this thread I've learned that I was conflating DPAF as a focus system with the tech which makes it possible, that is, a dual-photodiode CMOS. Since my IQ problems involve images taken through the viewfinder, "DPAF" is not involved, though the dual-photodiode CMOS might be. Thanks to posters here, especially Neuro, for helping sort out the confusion, and CPS for further clarifying and being open-minded about issues with the newer CMOS tech deployed in the 5DIV, 80D, 7DII and others.]

With both the 80D and 5DIV, I've been noticing some IQ problems that seem to have no explanation. With shutter speeds in the 250-500 range being the ones most commonly effected. If camera shake, exposure issues, UV filters are ruled out as issues, with ISO at 400 or below...

Anybody else who shoots with a DPAF camera noticing shots that just miss being sharp, but can point to no known reason?

If so, any suspicion that signal processing or other DPAF issues could be involved?

I'm referring to problems with photos taken through the viewfinder, NOT LiveView.

 

[BillB]

Re: DPAF the Villain? (When all else ruled out)

With both the 80D and 5DIV, I've been noticing some IQ problems that seem to have no explanation. With shutter speeds in the 250-500 range being the ones most commonly effected. If camera shake, exposure issues, UV filters are ruled out as issues, with ISO at 400 or below...

Anybody else who shoots with a DPAF camera noticing shots that just miss being sharp, but can point to no known reason?

If so, any suspicion that signal processing or other DPAF issues could be involved?

I'm referring to problems with photos taken through the viewfinder, NOT LiveView.

Was an IS lens involved? I found that especially with the 28mm, I have to be careful to give the IS time to settle before I trigger the shutter. Haven't noticed it so much with other IS lenses. (I was shooting with a 5DII.)

 

[pwp]

Re: DPAF the Villain? (When all else ruled out)

Unless you disclose the your AF selection method, focal length and to a lesser degree sensor size (FF or APS-C) it's harder to help you.

It's most likely to be a simple case of miss-focussing. It happens to everybody. Even though you feel confident you've got a "lock" on your subject, sometimes it can still be a bit off. Particularly with some Sigma lenses but that's another whole story! Are you manually placing a single AF point on your subject or relying on the camera to select a focus point? One-shot or continuous AF? These all make a big difference depending on what you're shooting.

Also, if you're using longer focal lengths and wide open aperture, it doesn't take much to shift your focus point. Even breathing or swaying ever so slightly can do it. It might also be your shutter speed if you're using long focal lengths. At 200mm on my 70-200 f/2.8isII I really don't expect too good a keeper rate if I'm shooting at 1/250th.

Are you aware of the useful "rule-of-thumb" regarding shutter speed and focal length? This is a rough, though useful formula. As a minimum shutter speed for a given focal length, try to match the speed to the focal length.

16mm lens - 1/15sec.
24mm lens - 1/25sec.
50mm lens - 1/60thsec.
135 mm lens - 1/125sec.
200mm lens - 1/250sec and so on...

Regard these as handheld minimums. With steady hands and great care you can beat this guideline, but as a general rule when working intuitively and quickly, I tend to at least double these minimums. I simply get more keepers.

-pw

 

[YuengLinger]

Re: DPAF the Villain? (When all else ruled out)

Unless you disclose the your AF selection method, focal length and to a lesser degree sensor size (FF or APS-C) it's harder to help you.

It's most likely to be a simple case of miss-focussing. It happens to everybody. Even though you feel confident you've got a "lock" on your subject, sometimes it can still be a bit off. Particularly with some Sigma lenses but that's another whole story! Are you manually placing a single AF point on your subject or relying on the camera to select a focus point? One-shot or continuous AF? These all make a big difference depending on what you're shooting.

Also, if you're using longer focal lengths and wide open aperture, it doesn't take much to shift your focus point. Even breathing or swaying ever so slightly can do it. It might also be your shutter speed if you're using long focal lengths. At 200mm on my 70-200 f/2.8isII I really don't expect too good a keeper rate if I'm shooting at 1/250th.

Are you aware of the useful "rule-of-thumb" regarding shutter speed and focal length? This is a rough, though useful formula. As a minimum shutter speed for a given focal length, try to match the speed to the focal length.

16mm lens - 1/15sec.
24mm lens - 1/25sec.
50mm lens - 1/60thsec.
135 mm lens - 1/125sec.
200mm lens - 1/250sec and so on...

Regard these as handheld minimums. With steady hands and great care you can beat this guideline, but as a general rule when working intuitively and quickly, I tend to at least double these minimums. I simply get more keepers.

-pw

Thanks, pw, these are good standard suggestions. Note that I'm having the issue with both the 80D and 5DIV, so that would be aps-c and ff.

My question regards use of DPAF bodies with various L lenses, mostly 24-70mm II, 85 1.2mm, at varying aperture, and with the lens shake issues ruled out. Also UV filters off. It's not quite a blur, it's not quite an AF miss. Something else I've never encountered on the 5DIII with the same lenses, same shooting scenarios.

 

[langdonb]

Re: DPAF the Villain? (When all else ruled out)

I believe that DPAF only works with live view...you state "I'm referring to problems with photos taken through the viewfinder, not LiveView." So if the shots you are referring to are not using live view, how could the shots via the normal AF sensor be affected?

I must say that I have had many problems with a 7DII with soft/inconsistent focus problems and after sending it back to Canon twice, the problems were never resolved. Most shots were on wildlife with low contrast situations. And all were taken with no camera shake, bean bag support, with and without IS. The body is now for sale!

 

[BillB]

Re: DPAF the Villain? (When all else ruled out)

Unless you disclose the your AF selection method, focal length and to a lesser degree sensor size (FF or APS-C) it's harder to help you.

It's most likely to be a simple case of miss-focussing. It happens to everybody. Even though you feel confident you've got a "lock" on your subject, sometimes it can still be a bit off. Particularly with some Sigma lenses but that's another whole story! Are you manually placing a single AF point on your subject or relying on the camera to select a focus point? One-shot or continuous AF? These all make a big difference depending on what you're shooting.

Also, if you're using longer focal lengths and wide open aperture, it doesn't take much to shift your focus point. Even breathing or swaying ever so slightly can do it. It might also be your shutter speed if you're using long focal lengths. At 200mm on my 70-200 f/2.8isII I really don't expect too good a keeper rate if I'm shooting at 1/250th.

Are you aware of the useful "rule-of-thumb" regarding shutter speed and focal length? This is a rough, though useful formula. As a minimum shutter speed for a given focal length, try to match the speed to the focal length.

16mm lens - 1/15sec.
24mm lens - 1/25sec.
50mm lens - 1/60thsec.
135 mm lens - 1/125sec.
200mm lens - 1/250sec and so on...

Regard these as handheld minimums. With steady hands and great care you can beat this guideline, but as a general rule when working intuitively and quickly, I tend to at least double these minimums. I simply get more keepers.

-pw

Thanks, pw, these are good standard suggestions. Note that I'm having the issue with both the 80D and 5DIV, so that would be aps-c and ff.

My question regards use of DPAF bodies with various L lenses, mostly 24-70mm II, 85 1.2mm, at varying aperture, and with the lens shake issues ruled out. Also UV filters off. It's not quite a blur, it's not quite an AF miss. Something else I've never encountered on the 5DIII with the same lenses, same shooting scenarios.

Some reports have suggested that best sharpening settings for the 5DIV may be a little more aggressive than for the 5DIII. Maybe it is also true for the 80D?. Is this a consistent issue or intermittent?

 

[Mt Spokane Photography]

Re: DPAF the Villain? (When all else ruled out)

I believe that DPAF only works with live view...you state "I'm referring to problems with photos taken through the viewfinder, not LiveView." So if the shots you are referring to are not using live view, how could the shots via the normal AF sensor be affected?

That statement confused me as well, DPAF is not used with viewfinder shooting. I took his question to be asking if dual pixels were a issue.

There are probably a million or a lot more dual pixel cameras in use, I've never heard of a sharpness issue being attributed to that, but someone has to be the first to discover anything. There are so many who pour over the finest details of their images, I would have expected that issues would have been found the first week.

 

[hne]

Re: DPAF the Villain? (When all else ruled out)

Are you testing in single or continuous drive mode?
Canon cameras are configured at delivery to not await perfect focus on first image in a series. This confused me to no end when I first got my 70D, having the first image ever so slightly soft. I'm thinking you might have forgotten that you tweaked that setting on your 5DmkIII.

 

[YuengLinger]

Re: DPAF the Villain? (When all else ruled out)

I believe that DPAF only works with live view...you state "I'm referring to problems with photos taken through the viewfinder, not LiveView." So if the shots you are referring to are not using live view, how could the shots via the normal AF sensor be affected?

I must say that I have had many problems with a 7DII with soft/inconsistent focus problems and after sending it back to Canon twice, the problems were never resolved. Most shots were on wildlife with low contrast situations. And all were taken with no camera shake, bean bag support, with and without IS. The body is now for sale!

Here's the best explanation for the tech which I can understand; clearly DPAF is involved in every photo taken, through the VF or with LiveView, and with video.

http://www.learn.usa.canon.com/resources/articles/2017/intro-to-dual-pixel-autofocus.shtml

Yesterday I updated the firmware in my 5DIV to 1.04, and THEN tried to systematically reproduce the issues. Of course I cannot. Was it the firmware? Who knows, on tripod with a very still subject, and then "in the wild," I'm back to feeling confident. That doesn't make up for two bad sessions earlier in the month where I seemed to be having slight exposure problems and the issue with pixels seeming to be "out of phase."

Is it a kind of lens flare issue that plays badly with the DPAF? So that the two signals get slightly "out of phase"?

Those same kind of "bad" images have been popping up just often enough for me to feel unsure about both the 80D and the 5DIV, and as I review images from the past six months, it seems they happened mostly where I had side-lit scenarios.

In fact, I made a peace of sorts with the 80D, where the problem was happening more often, concluding that the 80D just wasn't up to morning/afternoon wildlife shots with my 100-400mm II; this was where I first encountered the odd IQ issue. When using the 80D for walk-around travel and family fun, it's great. (By "morning/afternoon," I mean where side lighting is a part of most every shot.)

BUT, just this morning I did install the first firmware update for the 80D, 1.02, available since February, 2017. I'm going to get back out there with it after it!

I was hoping to hear more from owners of DPAF bodies. Thanks, langdonb--I'm sorry you have not resolved your issues.

 

[Loswr]

Re: DPAF the Villain? (When all else ruled out)

Here's the best explanation for the tech which I can understand; clearly DPAF is involved in every photo taken, through the VF or with LiveView, and with video.

Sorry, but I don't see an 'explanation' there, merely an incorrect statement. DPAF stands for dual pixel autofocus, and is used in Live View and video shooting. DPAF is not used when shooting through the viewfinder, instead the dedicated phase-detect AF sensor is used for autofocus. DPAF uses data from the CMOS image sensor to achieve focus, and when looking through the viewfinder, the mirror is down and the image sensor is not exposed to light...therefore, it cannot possibly be used to achieve focus.

If what you mean is how Mt. Spokane interpreted your statement, i.e. that the dual picture sensor architecture is involved in every still and moving image captured, that's true. But stating that DPAF is used for all images is incorrect.

 

[unfocused]

Re: DPAF the Villain? (When all else ruled out)

I think this can be filed in the same spot as the "pause in production of the 24-105 II" and "big whites will be obsolete when mirrorless takes over."

Someone has too much time on their hands and likes to worry about things that aren't real.

 

[YuengLinger]

Re: DPAF the Villain? (When all else ruled out)

Here's the best explanation for the tech which I can understand; clearly DPAF is involved in every photo taken, through the VF or with LiveView, and with video.

Sorry, but I don't see an 'explanation' there, merely an incorrect statement. DPAF stands for dual pixel autofocus, and is used in Live View and video shooting. DPAF is not used when shooting through the viewfinder, instead the dedicated phase-detect AF sensor is used for autofocus. DPAF uses data from the CMOS image sensor to achieve focus, and when looking through the viewfinder, the mirror is down and the image sensor is not exposed to light...therefore, it cannot possibly be used to achieve focus.

If what you mean is how Mt. Spokane interpreted your statement, i.e. that the dual picture sensor architecture is involved in every still and moving image captured, that's true. But stating that DPAF is used for all images is incorrect.

Whoops! Sorry, Neuro, I forgot to paste the link from Canon USA which does say DPAF is involved in viewfinder AF, and implies that the term is applied to the CMOS and processing system.

"For photographers and videographers who primarily capture fast-moving subjects — sports, wildlife, and/or children — DPAF can be a lifesaver. Get your subject in that 80% of the viewfinder, and let DPAF do the rest. Once you’ve indicated your preferred focal point — that speedy wide receiver sprinting down the field, that majestic eagle soaring above, your 5-year-old daughter performing her favorite dance routine — DPAF will track the motion and capture a crystal-clear still shot or video."

And...

"Each pixel on the CMOS imaging sensor has two separate, light-sensitive photodiodes, which convert light into an electronic signal. Independently, each half of a pixel detects light through separate micro lenses, atop each pixel. During AF detection, the two halves of each pixel -- the two photodiodes -- send separate signals, which are analyzed for focus information. Then, an instant later when an actual image or video frame is recorded, the two separate signals from each pixel are combined into one single one, for image capturing purposes. "

To say that DPAF is not involved in every shot, but only when AF is engaged, suggests that somehow during MF the camera shuts down one of the "two halves of each pixel."

Here is the link, and it's now up in my post too. Thanks!

http://www.learn.usa.canon.com/resources/articles/2017/intro-to-dual-pixel-autofocus.shtml

 

[chrysoberyl]

Re: DPAF the Villain? (When all else ruled out)

Hi YuengLinger. I am getting the same effect - neither front nor back focused, just out of focus. When focused manually, no problem. I did not know of the firmware update (thanks, BTW), and I will download that when possible.

 

[Loswr]

Re: DPAF the Villain? (When all else ruled out)

Whoops! Sorry, Neuro, I forgot to paste the link from Canon USA which does say DPAF is involved in viewfinder AF, and implies that the term is applied to the CMOS and processing system.

"For photographers and videographers who primarily capture fast-moving subjects — sports, wildlife, and/or children — DPAF can be a lifesaver. Get your subject in that 80% of the viewfinder, and let DPAF do the rest. Once you’ve indicated your preferred focal point — that speedy wide receiver sprinting down the field, that majestic eagle soaring above, your 5-year-old daughter performing her favorite dance routine — DPAF will track the motion and capture a crystal-clear still shot or video."

And...

"Each pixel on the CMOS imaging sensor has two separate, light-sensitive photodiodes, which convert light into an electronic signal. Independently, each half of a pixel detects light through separate micro lenses, atop each pixel. During AF detection, the two halves of each pixel -- the two photodiodes -- send separate signals, which are analyzed for focus information. Then, an instant later when an actual image or video frame is recorded, the two separate signals from each pixel are combined into one single one, for image capturing purposes. "

To say that DPAF is not involved in every shot, but only when AF is engaged, suggests that somehow during MF the camera shuts down one of the "two halves of each pixel."

Here is the link, and it's now up in my post too. Thanks!

http://www.learn.usa.canon.com/resources/articles/2017/intro-to-dual-pixel-autofocus.shtml

Sorry again, but you're misinterpreting the article. The '80% of the viewfinder' is in reference to this statement:

"On current models, approximately 80% of the viewfinder’s shooting area - both horizontally and vertically - is covered by DPAF...," in reference to the area of the sensor covered by DPAF photodiode pairs (actually, the whole sensor is covered with them, but the areas at the edges are not used for DPAF).

I find it odd that the article doesn't come right out and state it explicitly, but DPAF only works in Live View / Video shooting. That's implied at the end of the article, "No longer should the optical viewfinder be seen as the “right way” to take photos, nor should Live View be deemed an inferior function."

Think of it this way, you quoted the following: "During AF detection, the two halves of each pixel -- the two photodiodes -- send separate signals, which are analyzed for focus information. Then, an instant later when an actual image or video frame is recorded, the two separate signals from each pixel are combined into one single one, for image capturing purposes." When you're looking through the viewfinder and AF detection is occurring, the mirror is down and the sensor is not exposed to light. How is DPAF operating? It's not.

 

[YuengLinger]

Re: DPAF the Villain? (When all else ruled out)

Whoops! Sorry, Neuro, I forgot to paste the link from Canon USA which does say DPAF is involved in viewfinder AF, and implies that the term is applied to the CMOS and processing system.

"For photographers and videographers who primarily capture fast-moving subjects — sports, wildlife, and/or children — DPAF can be a lifesaver. Get your subject in that 80% of the viewfinder, and let DPAF do the rest. Once you’ve indicated your preferred focal point — that speedy wide receiver sprinting down the field, that majestic eagle soaring above, your 5-year-old daughter performing her favorite dance routine — DPAF will track the motion and capture a crystal-clear still shot or video."

And...

"Each pixel on the CMOS imaging sensor has two separate, light-sensitive photodiodes, which convert light into an electronic signal. Independently, each half of a pixel detects light through separate micro lenses, atop each pixel. During AF detection, the two halves of each pixel -- the two photodiodes -- send separate signals, which are analyzed for focus information. Then, an instant later when an actual image or video frame is recorded, the two separate signals from each pixel are combined into one single one, for image capturing purposes. "

To say that DPAF is not involved in every shot, but only when AF is engaged, suggests that somehow during MF the camera shuts down one of the "two halves of each pixel."

Here is the link, and it's now up in my post too. Thanks!

http://www.learn.usa.canon.com/resources/articles/2017/intro-to-dual-pixel-autofocus.shtml

Sorry again, but you're misinterpreting the article. The '80% of the viewfinder' is in reference to this statement:

"On current models, approximately 80% of the viewfinder’s shooting area - both horizontally and vertically - is covered by DPAF...," in reference to the area of the sensor covered by DPAF photodiode pairs (actually, the whole sensor is covered with them, but the areas at the edges are not used for DPAF).

I find it odd that the article doesn't come right out and state it explicitly, but DPAF only works in Live View / Video shooting. That's implied at the end of the article, "No longer should the optical viewfinder be seen as the “right way” to take photos, nor should Live View be deemed an inferior function."

Think of it this way, you quoted the following: "During AF detection, the two halves of each pixel -- the two photodiodes -- send separate signals, which are analyzed for focus information. Then, an instant later when an actual image or video frame is recorded, the two separate signals from each pixel are combined into one single one, for image capturing purposes." When you're looking through the viewfinder and AF detection is occurring, the mirror is down and the sensor is not exposed to light. How is DPAF operating? It's not.

"Get your subject in that 80% of the viewfinder, and let DPAF do the rest." This is pretty direct, and I can't strain my logic circuits hard enough to see how it can mean anything other than DPAF is involved in viewfinder captures. Suggesting that LiveView is catching up with viewfinder performance doesn't seem to imply otherwise at all.

Now if separate diodes are capturing data and then merging them together, whether calling this part of the "DPAF System" is correct or not--maybe "dual diode"?--then there is a processing step to put the info back together. This is the discussion area I'm interested in--when all other factors are ruled out, are some images being negatively impacted when things do not go perfectly right?

If this thread does nothing more than help us understand more about what Canon touted as groundbreaking tech, I'm very happy to be reading along!

And if it helps some of us who can find no other reason for certain IQ problems only noticed on DPAF bodies formulate questions for Canon service, all the better!

NOTE: I'm calling CPS to ask...

 

[Loswr]

Re: DPAF the Villain? (When all else ruled out)

"Get your subject in that 80% of the viewfinder, and let DPAF do the rest." This is pretty direct, and I can't strain my logic circuits hard enough to see how it can mean anything other than DPAF is involved in viewfinder captures. Suggesting that LiveView is catching up with viewfinder performance doesn't seem to imply otherwise at all.

Ok, I'll try once more then give up. You can choose to (mis)interpret a non-technical puff piece touting the advantages of DPAF, or try common sense. DPAF's full and proper name is "Dual Pixel CMOS Autofocus", because it uses the CMOS image sensor. When you're looking through the viewfinder, the CMOS image sensor is blocked and does not see the image. If the sensor can't see the image, it can't focus. Period. What you're suggesting would also mean that you could look through the viewfinder and see the live image on the camera's rear LCD at the same time. You can't, becuase of the mirror - for VF the mirror is down and for live view the mirror is up.

If common sense doesn't work, try Canon Europe, who state it explicitly:

[quote author=Canon Europe]
What is Dual Pixel CMOS AF?
A Canon breakthrough sees twice the amount of photodiodes on the sensor, allowing phase-detection AF on the imaging sensor’s surface for the first time. Dual Pixel CMOS AF is a sensor-based, phase detection Auto Focus (AF) technology designed to provide smooth, high-performance focus tracking in movies and fast autofocus acquisition when shooting still photos in Live View mode.
[/quote]

Regardless, you're right that even though DPAF isn't used when shooting through the VF, the underlying dual pixel architecture is present on the sensor and could, in theory, somehow affect the image. It really depends on how the camera handles the data – for image capture, are the signals from the paired photodiodes combined as analog or combined as digital? If it's the former, then you shouldn't have any potential for IQ effects. If it's the latter, I suppose some odd effect is theoretically possible. I have no idea how it's stored. At least on the 5DIV (but not on the 80D), you can shoot dual-pixel RAW files where the paired photodiodes are treated somewhat separately. That could be because the values for each sub-diode are stored separately, or perhaps a single value (from analog) is recorded, along with a separate 'offset' value that represents the phase difference between the two sub-diodes.

 

[unfocused]

Re: DPAF the Villain? (When all else ruled out)

...You can choose to (mis)interpret a non-technical puff piece touting the advantages of DPAF, or try common sense.

I was all set to make a snarky comment...but...decided to ask a real question instead.

Has anybody actually tried shooting action using live view and DPAF? I'm just having a really hard time imagining it would really work as well as this "puff piece" claims. Neuro, you've done some great bird-in-flight shots, have you tried using live view?

(Plus, it seems like it would be incredibly cumbersome to try to focus with a touch screen while holding a camera with a long lens mounted -- would be pretty much limited to tripod shots I would think.)

 

[Loswr]

Re: DPAF the Villain? (When all else ruled out)

Bring on the snark!

I haven't tried DPAF for tracking birds, but that's because my cameras don't have it. If they did, I'd at least have tried it. I do agree that it would be combersome for long lens shots unless the lens was on a gimbal.

 

[Mt Spokane Photography]

Re: DPAF the Villain? (When all else ruled out)

...You can choose to (mis)interpret a non-technical puff piece touting the advantages of DPAF, or try common sense.

I was all set to make a snarky comment...but...decided to ask a real question instead.

Has anybody actually tried shooting action using live view and DPAF? I'm just having a really hard time imagining it would really work as well as this "puff piece" claims. Neuro, you've done some great bird-in-flight shots, have you tried using live view?

(Plus, it seems like it would be incredibly cumbersome to try to focus with a touch screen while holding a camera with a long lens mounted -- would be pretty much limited to tripod shots I would think.)

I've tried it on several cameras, and so have testers. Compared to phase detect, it is much faster, not as fast as phase detect thru the viewfinder, but fast enough for the average person's use.

Where it really shines is autofocus and tracking during video. (90%) of the article is describing video) I have never used video on my dslr, because it wiuld be casual video, not setup on a tripod with aa focus puller, or measured distance to subject.

The AF shines for those who take videos of fast moving subjects where there is no rehearsal, and the autofocus allows you to concentrate on keeping the subjects in the frame.

The entire topic has been brought into question by the admission that the problem occurs during use of the viewfinder which totally rules out DPAF autofocus.

The issue with the referenced article is that it tells you how DPAF works, but not when it works.

This Canon Europe article includes when it works.

http://cpn.canon-europe.com/content/education/technical/eos_70d_technology.do

"Why was Dual Pixel CMOS AF developed? With the ability to make a subject stand out with a limited depth-of-field, comes a requirement to keep control over focus, if the main subject moves or the point of focus changes. Dual Pixel CMOS AF was developed so that control of focus during movie making is made easier and smoother – removing the perceived notions that a DSLR’s movie mode is usable only to a professional. Additionally, Dual Pixel CMOS AF was developed to enhance the usability of shooting with Live View – moving even closer towards the same performance encountered when using the viewfinder.

 

[YuengLinger]

Re: DPAF the Villain? (When all else ruled out)

Ok, Neuro, here is what Canon CPS says. They agree with you about DPAF being used only during LiveView or video, and they also agree that the article is poorly worded. Actually pledged to correct the article.

So I was wrong to use the term "DPAF" to discuss the issue that is popping up, but the CPS tech says that the dual photodiodes COULD hypothetically be involved in occasional problems, but hasn't seen complaints or reports about it.

Note that the 5DIV has one important extra feature not found on the 80D, the ability to choose DP Raw, essentially keeping both images recorded by the dual-photodiodes in a single file. (From what I understand, software exists which allows access to both images independently.)

He said the 5DIV captures with two photodiodes, creating two actual images that are then synced back together in-camera.

Which makes me believe that my original question is valid and relevant, though I should not have confused DPAF focusing with the dual-photodiode CMOS.

If things don't go perfectly right with the processing which syncs the two images back together, then, hypothetically, if all other errors are eliminated, the new tech misleadingly lumped under the name "DPAF" might be involved.

CPS wants me to email RAW files where I've noticed the problem, as well as RAWs captured in the same session where there is no problem.