>For you camera, I have some questions:
>- Do you have lenses that you trust to be correctly
>calibrated, and are they fine for the central sensor at 0 ?

I have a fair amount of glass, and while some come in at zero they are a minority. These are from old notes (I have done some more tuning), but I think I have:

14-24/2.8, AF=+10
24-70/2.8, AF=9
70-200/2.8, AF=2
85/1.4G, AF=+13
200/F2, AF=+11
200-400/F4 VRI, AF=0
200-400/F4 w 1.4x, AF=0

I'm definitely not one that believes that non-zero means bad, provided I have headroom to hit the right value.

>- How big is the difference in between the central and the
>outer sensor? I mean, what is the difference in between the
>optimal AF Fine Tune for the sensors?

The only one I checked the left/right points was the 85/1.4G. The number above was an average. The actual numbers were:

Left = + 2
Center = + 18
Right = +5

On paper that sounds horrible, but the shape of the curve for the left and right were pretty flat, so picking an average of +13 yielded an acceptable compromise. And in fact I couldn't really tell a difference in left and right by eye.

I believe left/right/center should be nearly identical and they are not. But it was "good enough" that on all my other lenses I could not tell the difference by eye in real images. Only on the 85/1.4 is it an issue, and only very slightly. I have not tried comparing inside and outside (but I use the tuned lenses both places without any apparent difference).

If you are expecting to be able to measure exactly the same value for left/right/center, my GUESS is you will never get there. I think the tolerance is beyond Nikon. But I think they CAN get it close enough that real images are OK. It doesn't sound like they did for you.

Linwood

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