"10D has a built-in database for each lens type..."

Started Jun 5, 2003 | Discussions thread
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Mishkin Veteran Member • Posts: 3,654
"10D has a built-in database for each lens type..."

"...that allows the camera to modify the commands that are sent to the lens to initiate focus drive."

  • a quote from Chuck Westfall's post:

http://www.robgalbraith.com/ubbthreads/showflat.php?Cat=&Board=UBB8&Number=139009&page=0&view=collapsed&sb=5&o=&fpart=1#Post139414

Interesting stuff.

1. Are 3rd party lenses in that database? A little scary for Sigma/Tokina/Tamron, isn't it? We've seen some compatibility issues already.

2. Yet another proof that lens is not a dumb device responding only to "focus farther... focus closer... stop!" commands. It's much more sophisticated than that. Another hint, from 24-70L technical report: "the autofocus (AF) algorithm is improved, resulting in even faster AF speed than its predecessor EF28-70mm f/2.8L USM". ( http://www.canon.com/camera-museum/tech/report/200301/report.html ). There's some algorithm programmed in lens' processor. Not just a motor responding to + - signal. Can older lenses be reprogrammed with newer, better "algorithms"?

3. All this returns us to those reports about Canon technicians saying that some [older] lenses need adjustment for 1.6x crop (or small pixels, whatever). I wonder if 50/1.4 needs this adjustment. When I set 10D to AI Servo with 50/1.4, it constantly moves (with a constant loud noise), with rather large magnitude, which suggests 50/1.4 has too coarse a focusing (at least, per its chip code as it is) for 10D. Doesn't happen with e.g. 70-200IS. Has anyone noticed this with 50/1.4? Has anyone improved 50/1.4 by sending it to Canon with 10D?

In one word: What's going on? How EXACTLY AF works? How body and lens interact with each other, what do they talk about?

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Mishkin

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