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Old Apr 29, 2003, 10:58 AM   #1
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Default 10D Focus Lemon

As you may have read, I had an awful time getting my new 10 D to have crispy focus. I tried many things from different lenses to only using the center focus area to sacrificing a chicken. At last I went in to the store and used the USM IS lenses and finally the L series lenses and STILL had focus problems. I understand that Canon will accept your body and lens to "fix" the problem, but I have Sigma lenses (getting re-chipped as we speak) and Canon won't touch 'em. Plus I have real problems with having to get my NEW camera FIXED!!

The final solution that Cord Camera in Cleveland came up with is either I wait a few weeks for a new shipment to come in or exchange with their demo body that was only two weeks old. Since I proabably have put more exposures on my body that the demo and didn't want to wait I chose to swap for the demo - and all's good. It even focuses well with the bogus plastic mount 28-80 cheap lens.

I reallllly like this camera but can't believe Canon has such poor quality control. Be warned and watch out on your new 10D

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Old May 1, 2003, 5:04 PM   #2
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No offense, but when you were in the camera shop, did you try other 10D body on any lenses, and they have the same focus problem as well? and what menthod of AF did you use, have you ever try to use the one point (center) focus and lock on the subject before shooting? Just curious?
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Old May 1, 2003, 6:07 PM   #3
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Hey - no offence taken.

It was that very action that made me return my body. I shot one with my body then the same with the stores demo body and there was a clear difference in sharpness of focus. For all shots I was using the center focus area only (a detail that I can't believe is necessary) and the exact same f-stop and speed. This proved to be true with almost all the lenses I tried - a cheap plastic mount - the USM IS lenses and an L series. I feel lucky that the store even had a demo body. Most only have a waiting list.

Good luck and take care.
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Old May 1, 2003, 11:47 PM   #4
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Although the camera has 7 auto focus points, they are not all created equal. The center focus point is better.... Its called a "cross-type" AF sensor.

I found a general description of canon AF this from here:

But how it applies to the 10D is described here:

There is also something here:

Specifically this quote:
The sensor limit of the cross sensors is the f-stop at which the high-precision autofocus sensors switch from cross sensor mode to linear sensor mode. (ie: the cross sensors in these cameras require fast lenses to work in high-precision mode) The 1D and 1Ds have 45 autofocus sensors, all of which can detect horizontal and diagonal lines at normal precision when used with a lens of f/8 or faster. However they also have 7 cross sensors capable of high-precision focussing. Of this group of 7, the central sensor retains high precision down to f/4 or faster and the remaining 6 cross sensors require f/2.8 or faster for high precision.
So if that is true, it seems to me that it is better to focus using the center point whenever possible. I'm a little unclear on what "high precision" gets you. I believe that it means a more accurate AF system at hitting the spot 1/3 of the way into the Depth Of Field. (with 2/3 behind the focus point.)
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