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Old June 9th, 2017, 02:31 PM   #1
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C100 Mark II Auto-Focus Problems

Using our C100 Mark II with the standard EFS 18-135 lens, we're having an intermittent AF issue (although lately it's happening more and more). Sometimes the AF works fine, but many times the floating AF box (or boxes) will not show up when the camera is set to Continuous/Face AF/Face Only, and the lens is set to AF. When set to Face Priority (vs Face Only), the permanent box pops up and the auto focus seems to work fine. But many times we need it in Face Only mode because of the shot movement or composition, and it often does not work. Anyone else having this issue? If so, what did you do to correct it? TIA.
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Old June 11th, 2017, 07:33 PM   #2
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Re: C100 Mark II Auto-Focus Problems

The usual suspects for face tracking not working are:

1. Exposure (under)

2. Backlighting, bright objects in the background or contrasty background. Ideally the best situation is a face that is lighter than the background.

3. Face the camera just doesn't like. We find that light skinned girls with obvious makeup track beautifully almost all the time, and darker skinned men with deepset eyes are hard to track.

Occasionally, in the middle of a interview with my C300II, I've seen it just stop tracking all of a sudden. Usually I just wait for a break and restart the camera...

Facetracking also has problems with Clog2 on the C300II, which doesn't apply to you...but with this earlier iteration, perhaps Clog could be the problem?...just guessing here as I don't really know your shooting situation.

It is not at all unusual for face tracking to behave inconsistently though, so being aware of the parameters above can help increase the likelihood that it will function as you hope it would. If you're inclined to post some problematic clips, where it's losing or hunting for focus, that may help us identify whats going on.

Barry
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Old June 11th, 2017, 10:44 PM   #3
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Re: C100 Mark II Auto-Focus Problems

Thanks for the info, Barry. We're not using Clog2; we're on the Cine1 gamma curve. I spoke with Canon C100 tech support yesterday. He suggested I update the firmware (we were 2 versions old), which I did. He also said that using the ABB once in a while might help. He said the pixel refresh on the auto black balance sometimes helps the AF perform better. I never heard that, but I gave it a try. We'll see if either idea helps. If not, I'll post some AF problem clips like you suggested. Thanks again for the feedback. Good to know we're not the only ones experiencing some AF problems here. --Jim
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Old June 11th, 2017, 11:26 PM   #4
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Re: C100 Mark II Auto-Focus Problems

Yeah...your camera doesn't do Clog2. And the Cine Gamma shouldn't cause any problems. The ABB theory is interesting, let us know if that does anything.

I think there's not really a "problem" with face detection, only that the algorithm they've written to recognize a "face" isn't perfect and isn't going to work in all situations. Keeping in mind the issues I mentioned at the top is your best defense.

Interestingly, Cloakroom media posted a face detection video on Vimeo from the C200 that would have been very challenging for your camera or mine. I do think they've improved the algorithm with each camera generation, and this new version seems the best yet.
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Old June 16th, 2017, 11:32 AM   #5
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Re: C100 Mark II Auto-Focus Problems

For what it's worth, I have had the EF-S 18-135 STM IS for three years and occasionally, when used on our C100 MKI or C300 MKI, the AF itself just stops working. It does it on both cameras so I think it's the lens. I pretty much only use one touch but when it stops working, I usually have to flip the lens AF to manual back and forth, remove and reseat the lens or power cycle the camera. It doesn't do it all of the time, I'd say perhaps 30% of the time, but it is really weird. None of my other Canon AF lenses seem to do this, it is isolated to the 18-135 STM IS. Slightly different issue than you are having. I black balance every shoot and every time I change the ambient environment. Another Canon quirk, the cameras seem to be really sensitive to BB, I've seen people record some whacked out colors if they don't BB. I recall in the "old days" I would go for months at time without black balancing with no ill effect on Sony and Panasonic broadcast cameras like the F900 and the tape Varicam.
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Old June 16th, 2017, 11:37 AM   #6
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Re: C100 Mark II Auto-Focus Problems

Thanks for the feedback, Dan. I spoke with Canon tech support on this. Very nice guy who seemed knowledgeable, but he said he's never heard anyone complain about this issue before. That surprised me because I've spoken to and emailed with others who have had this same problem. Wish there was a definite fix for it.
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