rscheffler
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 •Poll v3.1: MkIII have AF issues? | |
Jeff wrote:
Ron, how is your AI Servo tracking sensitivity set? I'd be curious to see if changing it to one click on the 'fast' side would change anything. I was getting a fair number of backfocused shots with the occasional front-focused shot as well, and moving one click to the fast side seems to have cleaned up that issue a bit.
Jeff,
It's set between slow and normal. I've played around with that setting somewhat and found for the field sports I photograph regularly, setting it to the faster settings has caused problems when a player is momentarily blocked by something closer to the camera. Even at the semi-slow setting, I've found the AF tends to jump rather quickly. If I remember, I'll give your suggestion a shot at my next football game. Over at the naturescapes forum, in the huge Mark III thread, one of the guys (LesZ) recommended BIF be done at the fast setting, which makes sense since usually a BIF is the closest object to the camera. I think I will probably use the fast setting for specific situations where I know the subject will usually be the closest object to the camera.
My CF III settings are: 2-semi-slow, 6-5, 7-2 (I've made adjustments for the 400 2.8, which seemed to have helped somewhat), 8-2, 10-1 and 16: set H to 9 fps, L to 8 fps. I usually shoot at 8 fps and it "seems" to improve results somewhat, though I have not made a controlled direct comparison against 10 fps. I've used 4-1 somewhat but am not convinced it made a difference. 5-1 I've found to be too dangerous for my liking, having been burned using it a couple times.
Way back in early June I commented on the AF problems I had photographing a triathlon with the Mark III. Some of it was due to poor AF point placement, but where I saw the greatest problem was with relatively slow runners in a backlit situation. AF was all over the place! At that time I had CF III-8 at 0. Setting it to 2 (I haven't tried 1) has since seemed to help, as has the aspect of the firmware update that keeps the AF from jumping to higher contrast information in the background.
I'd like to point out that I also had issues with AF accuracy in sports situations with the 1D Mark II and IIN. Backlit was usually a problem. In any case, it always produced more oof frames in a sequence than shooting with full sun on the subject (I like the look of backlit a lot, so endured the poorer results). This was what I immediately noticed with the Mark III at the triathlon in June, but that the initial results were considerably less consistent and focus was much farther off when it was off. Night sports also caused problems for the Mark II series, where often the fps rate would really slow down while the AF tried to track the subject, often with mixed results. Here I find my Mark III does considerably better and even though there are some oof frames, overall it produces a higher percentage of usable images. I feel the poor AF performance I've sometimes experienced with the Mark II series, and now the Mark III, have to some degree been caused by low subject contrast combined with less than optimal AF point placement. CF III 8-2 seems to have helped my situation and so has using off center AF points, which I previously rarely used for action because I found the non-cross type to struggle under fast paced situations. Yet even though these changes to how I set up and use the camera have improved the Mark III's results, it's now flawless, especially with the 400 2.8 for some reason.
A point I'd like to make is the need for each photographer to test the camera with a variety of lenses under a range of situations before coming to a conclusion. If I only ever used the Mark III with my 600 and not the 400, I would feel more confident in its AF performance. Even more so if I rarely shot sports or moving subjects in challenging situations.
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