Quote Originally Posted by neuroanatomist


I've thought about this method, but never tried it though it seems logical. One way you could test it, since the lens you tried seems to need nn adjustment, would be to apply increasing amounts of adjustment and see if/when you detect it as misadjusted. For reference, using the LensAlign I often find that 3-4 adjustment values look 'ok' (e.g. +1 to +3, so I just use the average); usually, a focal length/aperture combo with thinner DoF gives a tighter range. So, I'd think you'd want to see the effect by +3 or -3 for your lens (although more might not be bad as long as you can get a range and take the average - of course, you might get better accuracy with your method.

I think I will experiment using live viewwith the 24-70 lens tonight on the 5D Mark II. The lens has only been used once by my wife since I got it back from Canonafter I sent it in for service about 8 months ago. See if an average would work, then check it taking sets of pictures and do a comparison that way.


What got me thinking on this was that I wanted to do a mfa last week with the 7D in the field, because it seemed like it was back focusing on the 500mm F4L. ( I didn't have time to check the new camera before I left on my trip). I think in reality it was focusing just fine and the probelms I thought I was having were actualy my technique and learning the new AF system. It was dead on off the tripod at home.


It would seem logical to do it this way, in the field you could just set up on any point, do a focus and then a 10x check just to make sure you were hitting your target.