Nikon Denies All AutoFocus Problems

Started May 4, 2012 | Discussions thread
Ilkka Nissilä
Veteran MemberPosts: 4,107
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Re: Nikon Denies All AutoFocus Problems
In reply to Bruce Bracken, May 4, 2012

The manager's response seems polite and to the point. He's saying that (phase-detect) autofocus is not perfect and there is variability in the results and this is normal. I find that to find reasonable values for fine tune I have to do at least five test shots per fine tune setting and then plot them in a graph to determine the approximate crossing point with zero error. This works out nicely. Individual shots can still be slightly out of focus - that's the nature of the technology.

The manager offers that Nikon can have a look at your camera so he's not really denying the possibility that there's something wrong with your unit. I think this is quite reasonable.

The AF results of the phase-detect systems in DSLR from Nikon, Canon, Sony etc. all have variability in the results; Nikon to my knowledge has the smallest errors as a system. I recall a recent a study that was published online regarding this matter and the results were Nikon > Canon > Sony. I can't find it now but it was quite recent (last year or the one before?).

Here's what I would do. I would do this repeat-five times test that I mentioned with your target and vary the focus fine tune in steps of 5 to see if the error is systematic. Every other time displace the focus manually first to the front, and every other time to the back of the target so that the starting point doesn't affect the results significantly (I guess you should do six repetitions and not five so that it's even). I would then plot the errors and see if you have to adjust the camera. Then compare with another unit using the multi-cam 3500 system and see if the residual error (after fine tune) is greater with your D4. If it is then you may have cause for complaint. But based on any individual focus result you cannot say that there is something defective with your camera.

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