front focusing conundrum

Started Sep 8, 2008 | Discussions thread
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David Henneman
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front focusing conundrum
Sep 8, 2008

Hi all,

I recently picked up a 300 f/2.8L (non IS) at an estate sale. I plan to sell it but I wanted to make sure it functions properly before selling it so I sent in to Camera Clinic in Sparks NV for calibration. Canon no longer services this model lens so they referred me to several repair facilities that do these repairs.

Here's my conundrum:

I tested its autofocus, on the tripod, good light with 3 old print cartridges lined up. The lens consistently front focuses no matter which setting I use. Distance was about 30 feet.

I tested my 400 f/5.6L, and my 300 f/4L IS in the same manner and they were spot on.

I sent the lens in to have it properly calibrated and they found that the af was spot on, no problem at all. They could have easily charged me $200 to calibrate it but they didn't.

I used my canon 20d. I don't have another body to try it on and all my friends shoot nikon.

Anybody know what could be the problem?

thanks,
David

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