Has Nikon recalibrated your 85mm f/1.4G?

Started Nov 12, 2012 | Questions thread
just Tony
Contributing MemberPosts: 508
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Re: Has Nikon recalibrated your 85mm f/1.4G?
In reply to inasir1971, Nov 13, 2012

inasir1971 wrote:

Focus shift is a due to the design of the lens and thus is not a defect that can be fixed or repaired.

Yes; I mention that in the original posting.

AF Fine Tune allows the body to compensate for that behavior but only for a single amount of focus shift. The problem with focus shift is that there is a different amount of it for each different aperture setting... too bad the body accepts only one setting of AFFT that is going to be used at every aperture. Hence the problem.

However, the values that you are giving for the AF tuning are simply not possible - -1 for f/1.4, and +23 for f/4.

You can see the severity of the effect in the review at photozone.de. As the lens is stopped down the depth of field extends to the rear but not forward. It is indeed extreme and they identify it as a problem. The same thing happens in my 28mm f/2 AiS manual lens.

The difference is too great suggesting error, and more importantly it is suggesting that the focus shift is occurring in the wrong direction. Focus shift always moves the point of focus backwards requiring more negative AF fine tune, not positive as your figures suggest.

Perhaps the values that you have reached are caused by random AF error?

Good catch on my typographic error in my original posting! Thank you. You are correct: I should have written +1 for shooting at f/1.4 and -23 recommended (-20 is the closest available) for shooting at f/4.

I've had some lenses behave unpredictably (the 105mm f/2 DC for example). But the curves for the 85 1.4G were tight and reproducible at and near the peak. I'll post the results from FoCal and you'll see.

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