Sigma 70-200 f/2.8 EX DG HSM II front focus

I picked up a used copy of this lens at a good price and when I got a chance I broke out FoCal Plus to calibrate the MFA on my 7D and 50D.

Testing with the 7D indicated it was front focusing quite a bit, averaged out at +13 on the wide and long ends. Wasn't news to me since I had read lots of people experiencing front focus including the review at The Digital Picture (in his case, 3 out of 3 copies front focused). I was surprised that there wasn't any difference between MFA values at the wide and long ends, all the zooms I have tested so far had an average gap of +/- 10 between ends on this body.

When I put it on the 50D however, it started to get ugly. FoCal came back with recommended settings of +18 on the wide end and +22 on the long end. The latter obviously not being possible with maximum MFA adjustment available being +20. I've sent off an inquiry to Gentec in Canada to see how much it would cost to calibrate the lens.

I did send the seller a note to ask if he had focusing issues (my fault for not asking when I bought it) and he said it was spot on every time. Maybe he was just lucky with his setup as he never indicated doing any kind of MFA, but I find it a bit hard to believe.

Anyways, if anyone else has experienced focusing issues with this lens I'd like your input. Thanks!

Oh and I did get to try out the lens last night, #6, 7, and 8 in the thread below were shot with the 7D and Sigma combo. The rest were shot with the 50D and 85/1.8. I'll put it down to having a new piece of gear for now but I definitely had less keepers with the Sigma.

https://photography-on-the.net …/showthread.php​?t=1267948

Found I also had to switch off C.Fn III -4 (Lens drive when AF impossible) because a few times when I missed tracking a target the lens would hunt and was not able to reacquire.