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09-21-2018, 08:58 AM   #1
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Autofocus Accuracy across brands - any data?

I found this older article (2011) on cross brand autofocus:

Auto-focus accuracy: a scientific cross brand analysis (guest post) - Nikon Rumors

The conclusion was that the lenses and the specific camera bodies mattered more than brands. But that is very old and out of date. The K10D and K20D were the Pentax bodies examined. Surprisingly (to me) the K10D performed better than the K20D in this respect.

More important perhaps was the clear indication that fast lenses are not terribly accurate in their focusing due to the design of the autofocus systems. Given the industry trend towards bigger better corrected and faster lenses - do we think this will change? Has it already changed? Are f/1.4 or faster PDAF points likely to come into vogue? How does the mirrorless system world cope with this? Are their on sensor PDAF sensors limited or freed of any restrictions placed on DSLRs? I read an article that suggested that f/2.8 sensors far from the center of the frame were hard to implement due to the AF Submirror and design limitations of covering the entire exit pupil when viewed far off axis. Is this no longer a consideration in PDAF on sensor? What are the other concerns with PDAF on sensor?

09-21-2018, 09:33 AM   #2
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The article is old, but the conclusion remains valid: it depends on bodies and lenses used...

Now, although the trend is to go toward large aperture lens, the trend is also to move toward mirrorless cameras. Since they work with contrast focus, they're not limited by the aperture in their precision and accuracy. Their phase detection part is only there to provide a speedier focusing and better tracking, since PDAF has the advantage of providing information on distance. So, it's now more like an hybrid system where PDAF helps going rapidly near the point of focus while CDAF helps nailing it perfectly once near that point.

So, no, now that all the major players move toward mirroless I don't think we'll see much more than what we already have in PDAF technology. The efforts will rather be put on improving on sensor focusing. And, by definition, any issue related to mirror or submirror aren't relevant in a mirrorless camera. Or, said otherwise, on ML edge focusing is basically just as good as the center.

Last edited by CarlJF; 09-21-2018 at 09:39 AM.
09-21-2018, 09:40 AM   #3
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QuoteOriginally posted by CarlJF Quote
The article is old, but the conclusion remains valid: it depends on bodies and lenses used...

Now, although the trend is to go toward large aperture lens, the trend is also to move toward mirrorless cameras. Since they work with contrast focus, they're not limited by the aperture in their precision and accuracy. Their phase detection part is there to provide a speedier focusing and better tracking, since PDAF has the advantage of providing information on distance.

So, no, now that all the major players move toward mirroless I don't think we'll see much more than what we already have in PDAF technology. The efforts will rather be put on improving on sensor focusing.
I don't subscribe to the idea that DSLR's are dinosaurs - I think additional advancement will continue but I do see your point. If PDAF/CDAF hybrid af systems are more accurate with fast lenses then the pressure to develop better PDAF for DSLR's may be reduced and development in this area may lag.
09-21-2018, 09:55 AM   #4
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QuoteOriginally posted by UncleVanya Quote
I don't subscribe to the idea that DSLR's are dinosaurs - I think additional advancement will continue but I do see your point. If PDAF/CDAF hybrid af systems are more accurate with fast lenses then the pressure to develop better PDAF for DSLR's may be reduced and development in this area may lag.
Exactly. And the fact that on sensor focus still has a lot of things that could be improve or developed in a very competitive field while PDAF on DSLR is a very mature technology without as much competition. Now that Canon and Nikon are fully in the mirrorless game, I suppose they will put much more effort to compete in this technology rather than investing in PDAF where only minor iterations are possible. But I may be wrong...

09-21-2018, 11:46 AM   #5
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Today's mirrorless cameras are more accurate than DSLRs though I think the difference is overstated a little. The cool thing about mirrorless is that no focus microadjustments are necessary. However, focus adjustments aren't that hard to do either and I think with DSLRs we will see some developments like auto-adjusting (like the Nikon D850) but maybe with more advanced machine-learning algorithms.

I think there will still be some resources poured into DSLR research and advancement with regard to autofocus, but it seems like the market is shifting and lots of people are switching to mirrorless. I happen to like my DSLR, as I like nature photography and I can look through the lens while the camera is in standby mode and not have to use up battery power to do so...I do this a lot to identify bird species. That way I don't have to carry around binoculars. With an EVF, that would use battery power to do. Also with regard to wildlife, mirrorless cameras don't have as many native long lenses.

What I am pretty confident about is that in my lifetime, I think I will surely have to switch to a mirrorless camera.
09-22-2018, 11:19 AM   #6
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QuoteOriginally posted by automorphism Quote
What I am pretty confident about is that in my lifetime, I think I will surely have to switch to a mirrorless camera.
Sad to say, I think that's true. As much as I prefer the view though a true SLR viewfinder, there's no denying that eliminating the mirror mechanism, prism, and separate AF module will make cameras cheaper to make (even if they don't end up much cheaper in the stores).

And cheaper, always, always, wins out.
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