After reading "This lens is soft" and other myths by Roger Cicala, I decided to bone up on the micro adjustment feature for my Canon 5D Mark II. Essentially, this is designed to correct minor focusing problems. You may have heard the terms "front focusing" or "back focusing." It means that the lens and the camera are not in perfect focusing alignment. According to Cicala, many pro bodies, including the Canon 7D, 1DIII, 1DsIII, 5DII, 50D; Nikon D3, D3x, D300, D700; the Pentax K20D, the Olympus E-30 and E-620 have a microcalibration feature that allows you to better match problem lenses to the camera bodies.
The owner's manual for my Canon 5D Mark II cautions, however, that using micro adjustment should be the exception, not the rule.
"Normally, this adjustment is not required. Do this adjustment only if necessary."
That being said, if you have a camera that provides micro adjustment, and you suspect that a particular lens could use a little correction, you might want to investigate this further.
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I've just recently fiddled with the AF Fine Tune on my D300, and it's been interesting to see the results. I shot tethered into Aperture and compared the images at 100% (sometimes 200%) as I adjusted the fine tuning adjustment. In every case just a couple of ticks up or down the scale made a small but noticeable improvement in focus sharpness. I haven't gone through my entire lens lineup yet and can't draw any overall conclusions as to which lenses need it the most, but it does improve sharpness, particularly at wide apertures (1.4 to 2.0 for several of my lenses). I intend to check the results with the new 70-200 2.8 when I can get around to it, just out of curiosity.
You make a good point, Nelson, whether you intended to or not: This can be a time consuming process. Thanks for reporting on the D300, since I don't have access to that camera. And glad you saw some improvement!
You are right, people should listen to what you are saying because are absolutely right. :-D
You are right, people should listen to what you are saying because are absolutely right. :-D