Temporary process while we wait for Nikon to advise on D800 focus issues

Started May 4, 2012 | Discussions thread
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jonstatt
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Temporary process while we wait for Nikon to advise on D800 focus issues
May 4, 2012

This advice may be useful to others. While we are waiting for Nikon to have a proper, reliable fix. After 2500 shots messing around (thank goodness the shutter is good for 200,000 shots!), I have dialled in my lenses as best I can.

I believe my camera has a tendency to backfocus slightly in general because all lenses that were dialled in were negative numbers if anything.

I have got all my lenses usable with even the outermost points work in all but extreme circumstances as follows

105DC F2 - No problems at any points. No fine tuning needed (this lens normally front focuses)

105VR F2.8 - No problems at any points. A fine tuning of -5

80-400VR - No problems at any points. No fine tuning needed

28-70 F2.8 - No problems at any points. No fine tuning needed

14-24 F2.8 - No problems at any points up to about 20 feet. Leftmost points okay up to 40 feet at 24mm but slightly soft at 14mm. A fine tuning of -16

50 F1.4G - No problems at any focus points up to 10 feet. Leftmost points okay at longer distances at F2.8 and beyond but slightly soft at F1.4. A fine tuning of -8

So how did I achieve this? Here is the process

1) Using something like Lens Align or Spyder Lenscal, optimise the centre AF point such that it is exactly in the middle of the DOF. Use the widest aperture for this, and a distance of about 25x focal length. Compare against a liveview version of the same picture to ensure it is identical. This gives you, your frame of reference starting point fine tuning.

2) Now, take a picture using the leftmost AF point. Then follow this with an identical picture using Liveview

3) Keep adjusting the fine tuning (higher negative number) until you get the leftmost AF point to be the same as the liveview version

4) Go back to the centre focus point and see if it still within DOF or now softer. If softer, adjust fine tuning back until you find the point that just brings you back into DOF.

This will be the optimum position. For my camera at least, as you can see, I can get close to correct for all but the two most challenging lenses in my collection and even then, would rarely hit the problems in actual shooting. This is because I think outside focus points are rarely used on the 14-24 for most shooters...and its only out on the far left point at near to 14mm. And for the 50mm at longer distances you would probably be closing that aperture down beyond F1.4, or if not, would be near the centre for the subject.

Note, I had to get hold of a second copy of the 50mm lens to get to this point. The first sample was problematic on this camera no matter what I did, resulting in soft leftmost images even at F4 and beyond. This was most likely due to focus shift, which can vary a bit from lens to lens, and this technique relies on setting the centre to be the front of the DOF. On the D700 I didn't have this challenge so its not a bad lens as such.

Nikon D700 Nikon D800
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