Cam looks to be front focusing...is a small amount acceptable?

Heard of a few people complaining of their 40D's front focusing so I did a bit of a test. Now I did the same test w/ my old Xti w/ the same lens and focus was dead on. So I'm pretty sure that the lens is good.

At about 20 inches away, looks like it's front focusing about 2mm. Is this acceptable or SHOULD it be dead on? Thanks

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AF is never precise, if for no other reason than the limited precision with which the AF motor can move the lens. There will always be some plus and minus around the optimal focus. The best that can be achieved is that the average result coincides with the optimum, and the range is not excessive. To assess this, you'll need more than a single test. Do 10 or 20 at least, with the lens starting from focal positions both ahead and behind that of the target. Then you can be in a better position to gauge the mean and variance, and then it may be clear if the lens (or camera, or both) are out of specification or not. If so, get them serviced, if not, it's over to you; it may be in spec., but still unsatisfactory from your viewpoint, and it may or may not be feasible to have the lens corrected further.

Edit - Apologies to grammarians - sorry about the mixed noun number in this - singular/plural etc.

It's completely unacceptable if you are a professional 100% Crop Focus Chart photographer.

The guy that came up with this focusing chart should be put away! All the angst and hand wringing that it has caused is nothing short of amazing.

Aw, come on, focus charts are a great tool. How better to diagnose a problem than with a clear and simple standard. I mean, how many boxes can you analyze asking the same questions, “does my box look OOF?”. This focus chart is usually one of the first pics I take either with new body or lens. I like to run the equipment though its paces and insure everything is as it should be. Then when I start getting questionable results in the field I have nothing to blame except for me.

personally i'd line up 3 similar objects with one slightly in front of the middle on and one slightly behind and see if when you shoot the middle object with aperture wide open that is the sharpest. I use this test in shops when buying gear.I had a 350D that failed this test (sharpest area was always front object) and Canon recalibrated it which made all the difference.If there is a problem make sure its not the lens by trying two lenses.

This test looks pretty good to me.

So what's the verdict? I have done the test w/ two prime lenses and same results. Looks to be about 2-4mm front focus. Is this ok or should it be dead on?

cowboylife wrote in post #4107637
So what's the verdict? I have done the test w/ two prime lenses and same results. Looks to be about 2-4mm front focus. Is this ok or should it be dead on?

If it is consistent across lenses and repeatable, then it looks to be a body issue, and if it is consistently bad, it should be able to be tweaked to become consistently good.

Whether it is acceptable or not is an individual judgement call. Personally, I wouldn't be happy and would send it off for calibration under warranty; others would just stop down to f/8 and let the DoF take care of it. Note that I'd have it calibrated, not replaced with a new body; if I replaced it, I could well be in the same situation again.