7D and Micro-Adjust focusing

Ok, new 7D owner here. Loving it. This is the first camera I have had, that is MA capable. I had done some focus tests with previous cameras - but as long as they were "in the neighborhood", it was good enough. After all, what was I going to do? I really scrutinized these this time.

What I found, on one of my zooms, was that it seemed to front-focus at one end of the range, and back-focus at the other. The middle seemed to be ok. Please bear in mind, this is very subtle.

Clearly, there is nothing specific MA can do about this - and it makes a kind of sense, from a lens design perspective. Certainly, if I tended to use one end of the range a bit more than the other, i suppose I could optimize that end a bit. Anyway.

My questions is: Is this typical, and have others found this same thing? I'm not thinking there is anything wrong here, or anything to worry about, but am looking to confirm.

BTW - of my half-dozen or so lenses, i found one that could use a bit of a tweak - the rest were ok.

Thanks

Jim

Jim,

the rule of thumb I've heard here at POTN, and it makes sense to me, is to determine what focal length a zoom lens takes the most shots at then microadjust to that focal length. For example, I used a 70-200 f/2.8L IS on my 7D. Since I shot nearly everything at 200mm using the lens, I microadjusted at that focal length.

dave

That was where my head went first....of course if I tune it to the far end, then the near end, which is a tiny bit off, becomes quite a bit off.


I guess we live in an imperfect world!

you also tend to have less DOF at the telephoto end, so I MA on that end.

But you're right - MA at the focal length and range that you typically use the lens for best results.