briansquibb said:
I understand why it *might* AF at f/8 because of the Kenko...I am skeptical that it was "like a champ".
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Any new news about Canon 1D X f/8 AF?
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I understand why it *might* AF at f/8 because of the Kenko...I am skeptical that it was "like a champ".
I understand healthy skepticism, so I made a demonstration video and have uploaded two RAW files. The video shows the AF in action and towards the end I even focus on a moving jet after taking off, though it was in One Shot AF. Could have had a better result in Servo. Anyway, everything I was shooting was pretty far off. I should also test it on closer subjects with more complicated backgrounds. Let me know if there any specific scenarios you would like me to test. I suppose I can try the same extender stack on my 70-200 f/2.8 L IS II and see if works...in fact I'll go do that now, while you are chewing this stuff over.
Oh, regarding the Kenko fooling the body... the camera shows f/8 and the EXIF records that, so at least at some level, the camera is aware.
video:
http://youtu.be/Q42Ppq6U63k
two RAW images:
http://dl.dropbox.com/u/32275661/9Z9C4459.CR2
http://dl.dropbox.com/u/32275661/9Z9C4464.CR2
Oh, regarding the Kenko fooling the body... the camera shows f/8 and the EXIF records that, so at least at some level, the camera is aware.
video:
http://youtu.be/Q42Ppq6U63k
two RAW images:
http://dl.dropbox.com/u/32275661/9Z9C4459.CR2
http://dl.dropbox.com/u/32275661/9Z9C4464.CR2
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Well, @bchernicoff, I can't thank you enough! 
That actually looked like it was rather difficult to record a video of the viewfinder while activating AF, so the effort is much appreciated. I'm pretty surprised by the speed, looks like it locked on pretty quick onto pretty much everything...so I have to agree...seems to focus "like a champ" (at least in that light!)
Any chance you could try some lower-light tracking at f/8? Just to see how it might perform in a more real-world setting.
Anyway, thanks again! Looks pretty awesome, and certainly good enough for birds in daylight.
That actually looked like it was rather difficult to record a video of the viewfinder while activating AF, so the effort is much appreciated. I'm pretty surprised by the speed, looks like it locked on pretty quick onto pretty much everything...so I have to agree...seems to focus "like a champ" (at least in that light!) Any chance you could try some lower-light tracking at f/8? Just to see how it might perform in a more real-world setting.
Anyway, thanks again! Looks pretty awesome, and certainly good enough for birds in daylight.
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I just tried it with my 70-200 IS Mk II in much lower light and with more complicated backgrounds just in case buildings at near infinity focus against the sky were too easy a subject... and the result is... Wow!
Another video...this one is less clear...parts of it black out as the cell phone camera looking through the viewfinder didn't get enough light, but stick with it. Also, I tried it indoors, handheld with just one lamp on and it works fantastic.
I was using Aperture to read the EXIF information and by default it doesn't show the lens's max aperture. I enabled that field and for the extender stack with 400mm f/2.8, it shows f/5.66, however the body will only let you select f/8, so there is definitely some Kenko trickery going on. All I know is it works!
http://youtu.be/sPgF4f_knz8
Another video...this one is less clear...parts of it black out as the cell phone camera looking through the viewfinder didn't get enough light, but stick with it. Also, I tried it indoors, handheld with just one lamp on and it works fantastic.
I was using Aperture to read the EXIF information and by default it doesn't show the lens's max aperture. I enabled that field and for the extender stack with 400mm f/2.8, it shows f/5.66, however the body will only let you select f/8, so there is definitely some Kenko trickery going on. All I know is it works!
http://youtu.be/sPgF4f_knz8
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bchernicoff said:
I have to agree, seems to be working like a champ! I'm curious...it looked like you were using all of the AF points there in full auto selection mode? If so, that is really quite impressive, as many of those points are f/4 only points, IIRC. Very impressive indeed. Thanks! I still want to wait and see what Canon comes up with for a megapixel monster as competition against the D800 (for my landscape work), but you've put the 5D III back in the running as a serious contender for my next camera body (vs. the 1D IV, which given its price point even used, is looking little bit less appealing now). I may have to grab a 1.4x Kenko and try it on my 100-400 until I can afford something along the lines of a 600/4 II. I've heard the same kinds of things about the 100-400 and f/8 AF just not being viable using a pin-taping trick, but I figure its worth a try (at least, with Canon's new 61pt AF system.)
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jrista said:
Just be sure to order the right model (DGX) and read the post people in which people have had problems with them. It seems like they possibly did a silent update that has increased compatibility, so I would recommend ordering one new from Adorama (I bought mine through Amazon but the order was filled by Adorama).
http://www.adorama.com/KN14XPEOSDGX.html
http://www.canonrumors.com/forum/index.php?topic=4977.0
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bchernicoff said:
Thanks for the links. I'm definitely going to check that out. I've been thinking about the way AF is rated, and why Canon may not want to rate their new AF system for f/8. Generally speaking, I think AF systems works with more infrared light than visible light, and as such, they are capable of functioning to very low exposure values. I think most of the time Canon AF systems are rated for -1 EV operation, while Nikon's newer AF systems are rated for -2 EV operation. I am curious if the f/8 AF "limitation" is only once you start to approach this limit. Based on your videos, f/8 AF certainly seems to work great when there is a decent amount of light.
I guess one could try to AF in full moonlight (which would be about -2 EV) on the 5D III or 1D X, or maybe a dimly lit room with dimable lights, etc. to see how f/8 AF works at those levels. I believe birds at or just after sunset are probably around 8-10EV, which is probably roughly the same as @bchernicoff's second video (maybe a bit darker), in which case f/8 AF and a Kenko TC with Canon's f/5.6 AF sensor is probably entirely viable for bird photographers.
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