I've finally got around to micro adjusting my 50mm f/1.4 on my 7D, which I had noticed was front focussing. I noticed this after photographing indoor theatre. I usually use the lens for close-up portraits , but for the theatre, i was 10-15 meters away from the stage.
I followed canon's advice, shot at 50 times focal length (2.5 meters), manually de-focused to infinity before each shot. I took three shots at 0, three at +5, then three at +10 etc...
After some testing with different values, the adjustment for +2 seemed the best.
It didn't seem much of a difference to the default zero, which surprised me because i was sure the lens was front focussing.
So i then went outside and tried this method on various flat objects (with good contrast) approximately 10 meters away. At the setting of +2, it was blurred.
After performing the same testing, i got reasonable results at +10, and slightly better results at +20!!!!
So I understand the setting only works for one focal length, and you should set it at the focal length you use the most, but is it too much to ask for a lens that can focus well regardless of distance, or is this acceptable behaviour?
I mean at least i now know if i want to shoot theatre again, change it to +15 to +20, and for closeups, take it back to +2, but that's hardly ideal when you are taking various shots at various distances.
PS. for those wanting to critique my testing methods, please go away as no-one wants a repeat of last thread