Originally posted by stevebrot What he said, though I would add:
- Get a screen with split image
- Shim only if needed and calibrate against live-view using a magnifying loupe. The AF system is much less precise than live-view or a split image screen.
- When doing calibration, use a flat, high-contrast target, camera on tripod, sensor parallel to target
Ah, people replying here might not realise that:
a) I have a split screen, hence playing around with shims
b) I fully understand that AF has nothing to do with focusing screens.
Id was due to playing around with the above that it became apparent that the AF confirmation was way off the actual focus (as in what appears in digital preview or the final shot). My issue is with AF is that even with max fine adjust, it's still 2cm off at 70cm with a 50mm lens. At f1.7 the dof is less than this. I confirmed my tests by using catch-in focus, first starting a infinity, then starting at min: The AF is quite consistent about when it considers focusing is reached.
To be sure I was focusing on a point on the same plane, I repeated the test with a target directly at right angles to the camera. After getting the optimum focus according to AF, I can move the target 2cm towards the camera and take another shot... which is pin sharp compared to where the camera's idea as to where focus should be.
If I had a fast AF prime it would be very obvious that the camera was FF - 2cm is huge when dof is so shallow.
F.