MFA tweak...How much is acceptable?

[HDNitehawk]

You have 14 more places before you get to -20. I don't think -6 is so bad. If it is brand new like you say, return it and get another.

[Sean Setters]

Read this, it's very informative. An MFA of -6 on your camera might be a +2 or 0 on mine. There are certain tolerances, and being able to adjust the focus via MFA was meant to address the variation in those tolerances. If it works at -6, keep it and use it at -6.

I did send back a third-party lens (two copies, in fact) because of focus issues, though. In that case, the lens required a [rather extreme] MFA with relatively close subjects, and a completely different MFA with farther away subjects. There was no way to reconcile the two, and I decided it wasn't worth the hassle.

Recently, though, I dialed in a -4 MFA on a lens I purchased used off of Ebay and it works absolutely perfectly for me. I couldn't be happier. This particular 28-70 f/2.8 L may be 10 years old, but I wouldn't trade it for anything, MFA and all.


Kailey Sue Fan 2 by budrowilson, on Flickr