AF Fine tune process & de-focus

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keisar New Member • Posts: 7
AF Fine tune process & de-focus

Hello,

Writing here today because i’m a bit desperate to find answers about AF Fine Tune.

My previous camera was a D700 (12MP) and obviously all lenses looks extremely sharp, this is quite different with my new D850.

Lenses are Nikon : 14-24 ; 70-200 f/2.8 ; 50 f/1.4 ; 35 f/1.8

The live view focus gives very good and sharp focus and I’m expecting the normal AF to gives similar results.

But it is not the case, results are good but can be better so I started AF Fine tune and here is how I proceed :

  1. Put datacolor mire & dslr lens on a tripod, level it
  2. Set up the distance (30 x focal lenght)
  3. Align everything
  4. Down one stop
  5. Defocus using the focus ring
  6. Focus with live view
  7. Press AF and red button
  8. Press OK & Go to AF Fine tune menu, note the value
  9. Set the fine tune back to zero
  10. Repeat from step 5. Do it 20 times.
  11. Take the list of the measures, remove the highest and lowest one. Make the average.

I’m not sure this method is the best, especially when I defocus (step 5). I notice that depending if I defocus clockwise or counter clockwise results with live view autofocus are different (picture) and obviously the value measured is different. Here the example of 14-24 but same for 70-200, 35 and 50mm.

Contrast detect auto focus results (cropped).

And here are my questions !! :

  1. Can you explain that (results after de-focusing clockwise or counter cw) ?
  2. Is defocus a good idea ?
  3. How do you guys proceed ?
  4. Can I really expect the auto focus results to be like live view (contrast detect) auto focus ?
  5. When do you decide to do AF Fine tune, do you accept some defaults ?

Thank you

Cesar.

Nikon D700 Nikon D850
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