Daan B
Offline
• • • • •
Upload & Sell: Off
|
 p.4 #10 · 1Ds3 + 35L: samples AF performance | |
Ok, some conclusions after having tested all the 19 AF points with the 35L, 24-70L and 85L II.
The 19 AF points show different behaviour with these three lenses. There are a couple of "bad" AF points that all lenses share (upper right corner for example), but there are a lot that are actually different between these lenses. All three lenses have an average of 9 AF points in total that are off. Also, it makes a difference shooting in vertical or horizontal mode with the same lens as to which AF points are off.
So it looks like every lens (and its shooting orientation) has a different effect on the 1Ds3 AF system. But if lenses share the same FL, the differences seem to be the least. There are more differences between 24-70L @ 35mm / 35L and the 85L II than there are between the 24-70L @ 35mm and the 35L in sharing the same "bad" AF points. But this could also be a coincidence.
With the 85L II, most mis-focus is covered up by the DOF by f/4 and sometimes by f/2-f/2.8. With the 24-70L @ 35mm and the 35L sometimes f/4 isn't enough to cover up any mis-focus. This could be related to what Henry suggested, that because of the larger DOF at wide angle focal lengths, and Canon uses an AF tolerance of 1/3 of the DOF at wide open, there is more room for the AF to mess up. OTOH, more room could theoretically also mean that the AF has more DOF to cover up it's mistakes.
With both the 35L and 85L II I also have experienced very large front focus issues... I mean, in a sequence all of a sudden the focus could be way off (like half a meter), while the next shot was good. Like AF hick-ups.
What next? If all lenses make the 1Ds3 react differently as to what AF points are off, it is useless for a tech to adjust individual AF points. I mean, when he adjusts one AF point for a certain lens, it could be way off with another, etc. And for all I know the AF points could very well be adjusted properly and something else is going on.
The last time I asked the tech to have a good look at some AF points that I had trouble with. Maybe he screwed up on these, or maybe there is something else going on, but afterwards I didn't notice any difference in AF performance on these specific AF points. Actually, overall I couldn't detect any differences at all. Points that were bad before adjustment, were also bad afterwards.
So, that leaves me with little hope that calibration of the body is an option to cure things. Unless it is possible to calibrate every AF point to any lens. But I know Canon Service calibrates all the 45 AF points of the body first, and than calibrates all lenses using only the center AF point of the body. And even then, maybe the cause of these AF problems is an entirely different one.
So I will see what the tech will conclude. Any next steps are based on his ruling. If he finds that there is room for improvement by calibrating or repairing it shall be done. If he thinks it is hopeless, it probably means a new camera. But do I really want that? At this moment maybe I'd rather have my money back... But this probably only happens when hell freezes over 
In the meantime, when I take the occasional AF hick-ups for granted, the situation is workable when I only use the center AF point with wide angle lenses and when I stop down a little when using the outer AF points of (medium) tele lenses. Of course MF is always an option, if the situation allows for it. Thank God for Live View in these cases...
I must say I am somewhat disappointed in the 1Ds3 AF. One of the reasons to give my 5D some rest, was because I wanted more accurate and reliable AF on the outer AF points with larger apertures. But guess what...? The 5D's AF kicks the 1Ds3's AF ass if it comes to using wide aperture lenses (on outer AF points). At this point I experience the 1Ds3's AF is limiting to my creativity and therefore my business. I find it hard having to bow down to the AF quirks of this "camera" because they are so inconsistent and unexpected.
However, I will give the tech another change and hope my collected data is of some use for him 
To be continued...
Edited by Daan B on Jul 06, 2008 at 09:05 AM GMT
Edited by Daan B on Jul 06, 2008 at 09:07 AM GMT
Edited on Jul 06, 2008 at 04:07 AM
|
