Reader D.S. in Ottawa, Canada writes in reference to Focus Accuracy:
I have just finished reading your excellent article about focus accuracy and backfocus on the D2X with wide aperture lenses. I have been looking for some explanations as for why my combo gives me consistently poor results (from 5-7mm off with a 50mm f/1.4 to over 10cm off with my 70-200 f/2.8.). I have done a lot of tests using all my lenses, and have discovered with horror that the camera only very rarely focuses spot-on. I have tried shooting hand-drawn paper targets, and obtained the same results: the camera always focuses 'after' the target. Oddly, when shooting portraits the effects are much less apparent, and the 50mm f1.8 lens gives me perfect focus every time. I have read on some forum that two adjustment screws exist on the side walls of the camera (mirror up) and allow the adjustment of both autofocus and manual focus by Nikon technicians. Should I send the camera back for repair, or is this problem common to all high-resolution D-SLRs?
Thank you for writing DS—I always like getting feedback from readers.
I’m reminded of my own experiences when I receive such emails (on a regular basis). I’ve experienced similar behavior, and it’s ruinous--you can “nail” a favorite moment but the shot turns out to be a throw-away with razor-sharp hair on the back of the head, but blurred eyes! Very frustrating. The much less expensive D200 has performed better for me than the D2x. See D200 vs D2x (paid review) for a specific example.
Yes, I strongly recommend sending the camera to Nikon service, ideally with 2 or 3 lenses (perhaps the 50 f/1.4D and the 70-200 f/2.8). Sometimes the problem is in the lens, and sometimes it is in the camera body. I’ve seen both situations.
One should also check that the lens mount is not bent. See Lens Mount Misalignment.
For checking backfocus (focusing behind the desired plane of focus), a “3D” target is extremely helpful. I created a target with 80mm of total “depth” for this purpose:
Certain older non-AF-S lenses, such as the 135mm f/2.0 DC and the 105mm f/2.0 DC are awful with their focus accuracy, apparently due to the clunky and slow mechanical focus. Newer AF-S lenses ought to be very accurate (though not perfect), and even the 50mm f/1.4D has been highly accurate (for me at least).
Note to DS: I was not able to reply due to a problem with your email address (email address and domain elided):
The following message could not be delivered to ____ because the domain DDDD.com has no valid MX records.