As the MKIII saga continues I had an opportunity to fully test my MKIII over the weekend. As some of you know I shoot R/C aircraft for several magazines. I went to a show where there were some R/C jets flying. Yes, real mini turbines that reach airspeeds of 250mph +. I knew this would be a great test for the MKIII servo autofocus. It is a more stringent test than Galbraith's sprinter.
In this series of shots the plane is traveling approx 100mph at the camera. All shots were shot at f2.8 and ss 1/1250th on a 300 2.8 lens using centerpoint only. I was able to keep the centerpoint focus on the jet for all 16 shots. The background was fairly busy as well. The frames begin at approx a 50% crop with the final shot at full frame. All shots in the burst are included and there are 2 out of 16 that are a tad soft. This is definitely better performance than I get with my MKIIn's.
I think this series shows that there are excellent performing MKIIIs out there. I know some are duds, but not all of them.
Mike - Love that tune! I would like to see long bursts of similar subjects from D3's and D700s - you don't often see long bursts, you just hear about how good other autofocus systems are. I have had good luck with my erratic small bird shots as well.
Very nice work.
My low serial MKIII with no fixes, wrestles a bit with busy backgrounds like that. Two or three series perfect the next poor. My MKIIn nailed them almost 100% of the time.
There are a few where the focus is not perfect but overall not bad. One thing is that Rob G's problem were mostly when using multiple AF focus points and as problematic with center point AF from my remembrance of his article.
Q. How do you know the autofocus settings dialed into the camera aren't the problem?
First, it's important to understand that most of the EOS-1D Mark III's autofocus options are personal preference settings. They provide ways to configure the camera to your liking rather than fundamentally change the way the system determines subject distance or commands the lens to move to a certain point of focus. In other words, serious autofocus problems aren't likely to be fixed by adjusting a few Custom Functions.
That said, our desire to properly understand EOS-1D Mark III autofocus, combined with a nagging feeling that there must be some way to get the darned thing to focus well, meant we threw logic out the window and began working through the various settings that might possibly help, maybe. To that end we tried enabling, disabling or otherwise fine-tuning these options:
C. FnIII-2, AI Servo Tracking Sensitivity (normal, Slow and in-between)
C. FnIII-3, AI Servo 1st/2nd Image Priority (all options)
C. FnIII-4, AI Servo Tracking Method
C. FnIII-5, Lens Drive When AF Impossible
C. FnIII-8, AF Expansion with Selected Point (Disable, Enable Surrounding Assist Points)
C. FnIII-16, Continuous Shooting Speed (10 fps, 8 fps, 3fps)
We shot most things using the centre AF point only, though at times we switched to a couple of the outer AF points or all 45 AF points. The result? The only setting that had any real impact on the basic character of the autofocus was C. FnIII-2, AI Servo Tracking Sensitivity. We'll talk about it next.
mark fadely wrote:
In this series of shots the plane is traveling approx 100mph at the camera.
Mark, if my math is right, that would come to close to 150 ft/sec. That is very fast and I suspect that kinda target might exceed any specs Canon might have had for the camera AF system.
If I read your post right, it would have taken you up to 2 seconds for 16 shots on high FPS, in which time the plane would have covered up to 300 ft.
Mike V wrote:
Wouldn't the models be much further away than the sprinter, so the depth of field a lot more, so much easier to nail focus?
The model is approx the same size as a person and the last frame is full frame so considering the speed and distance covered I would say the autofocus is more demanding on the plane than a sprinter. Your argument might be valid for the first few frames in the series, but not after that point.
That would be right Peter. Don't know about the autofocus specs but some of the velocity is reduced by the increasing shooting angle towards the end of the series.
PetKal wrote:
Mark, if my math is right, that would come to close to 150 ft/sec. That is very fast and I suspect that kinda target might exceed any specs Canon might have had for the camera AF system.
If I read your post right, it would have taken you up to 2 seconds for 16 shots on high FPS, in which time the plane would have covered up to 300 ft.
I see no any relationship or equivalence with RG's AF test results regarding Mark III's AI Servo performance.
Also for this kind of high speed moving subject, the shooting skill is more important than the camera's AF Servo performance. You did a great job in this 16 sequence shots.
Nice shots, and as others have said great tracking ability! To my eye four or five were pretty soft, but for that type of target that's impressive and it's nice to see that it's performing better than your 1d2n in similar shots.
It could be that for whatever reason the camera has a bigger issue with something that is moving slower than faster.
Since you kept the center point on the object the whole time, and with it's high speed there would be larger focus adjustments for the camera to sense and make as it was moving. Perhaps the problem is on slower objects like the sprinter where the focus variations from shot to shot at 10fps is very small.
I have the feeling that the problems Galbraith had with the sprinters had to do with pumping arms and constantly changing clothing contours. The plane presents contours that only change as its angle changes, which occurs in a pretty steady fashion. Since Mark did a great job of tracking it with the center point, the MkIII did its job (not perfectly, but very well). If the MkII really does have any advantage in tracking sprinters (or birds in flight), maybe it's because it doesn't react to minute changes in subject position quite as quickly as the MkIII does. That would also fit with RG finding that adjustments to C. FnIII-2, AI Servo Tracking Sensitivity were the only ones that affected his particular problem.
I don't have a lens comparable to the 300/2.8, but my MkIII with 100-400L tracks soccer players well, with a slightly higher hit rate than my MkII. f/4.5-5.6 is obviously not as demanding as 2.8, but the MkIII AF has been working fine for me.
Love that tune! I would like to see long bursts of similar subjects from D3's and D700s - you don't often see long bursts, you just hear about how good other autofocus systems are. I have had good luck with my erratic small bird shots as well.
