Originally posted by pschlute I have not tried the dot-tune method, but using the old fashioned method of a test chart at a 45 degree angle you should notice a very big difference between -10 and +10.
Camera on a tripod triggered either remotely or with 2 sec timer.
... (nice list of steps omitted for brevity)
Originally posted by pschlute ps. When you make an adjustment are you saving it as an individual lens AF adjustment or as a "global" adjustment that will apply to all lenses?
Yes, all good suggestions, and all those steps are what I have done. Like I said, I'm an engineer, and a stickler for details. The adjustments were done as individual adjustments. But as a test, I also reset all settings, and then redid all the tests with both global and individual.
But I think, now that I have done DimC's test, and saw that the camera couldn't achieve focus on some negative steps of adjustment, I think I understand what is going on. In fact, there probably is indeed a difference between the adjustment steps, visually, using a angled chart. BUT. I plan to use the 55-300 mostly at 300, and at 5.8 (maximum aperture of the lens at that focal length, too much DoF at that aperture, and of course not the sharpest aperture for the lens (DxOMark tests notwithstanding)) I don't think there was enough *visible* difference between the steps (at least for me), especially since DimC's tests confirmed some degree of back focus, and showed that I didn't have enough correction steps to fully bring the acceptable focus to 50% in front, and 50% in back.
All and all, this has been an interesting exercise, and I'm going to try some other of my lenses with DimC's test, only because the other tests -- 3 different kinds of angled tests, and the Moire test -- never really gave me the feedback that I was looking for.
I am interested in anyone else who has tried to focus-adjust a DAL 55-300 at 300, however, to see if they have a different result than I. But of course, different copies of the lens are going to focus differently, because I understand that while they are all acceptably within 'spec', there is a rather wide band of acceptability.