Shocking insight: AF is not a closed feedback loop!

Started Jul 18, 2003 | Discussions thread
OP Mishkin™ Contributing Member • Posts: 917
for now that you don't have 1Ds ;) just should remember that with 10D you may get SOME of the shots blurred by up to 4 pixels at f/2.8 (100% of 0.03mm CoC) and proportionally more at faster apertures (e.g. 8 pixels at f/1.4). I don't know the statistical distribution within this 0-100% acceptable accuracy. Hopefully, it has maximum at 0% (perfect focus, 0-pixel blur) and only a small tail at 100%. But some of the shots are almost quaranteed to be as blurry as described. And it's within AF spec!

With 1D/1Ds, theoretically things should improve by 3x. There still could be problems in f/1.0-f/2.0 range.

It's best just to know these limitations and learn how to deal with them. I for myself decided what to do when shooting in the 1.4-4 range - shoot a lot of frames while moving to your subject (when it's close) or rotating focus ring (when subject is too far). I'm going to use this technique extensively when shooting available light and not worry about AF giving me blurry images.

And L lenses are still great. Use them now (with knowledge), and enjoy your investment in the future when you will have a camera with much better AF.

Larry H. Smith wrote:
Up-front: I haven't read (and probably couldn't have followed) all
the tech-discussion on the AF "issue'"in the various threads.

Does this new understanding (Thanks mishkin!)make it possible to
put into some reasonable number of words , a "best" way for the
user to maximize the AF potential of his rig, ...or a best way to
test/adjust "whatever" for that "best" performance?

(I mean when using whatever f-stop the photog WANTS to use, for
image reasons other-than-focus.)

This whole "what the camera can/can't do FOR you" thing is the main
reason I won't be happy till I have a pro-level camera that will
let ME do what I want, with a viewfinder that CLEARLY shows me what
is happening.



Mishkin2 wrote:

...a lotta stuff!

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