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Tested left AF on D800: don't understand the results !

newbird

Neuville, near Quebec City, CA
2038 posts

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newbird Silver Member Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 25th Apr 2006
Mon 06-Aug-12 11:26 PM

Hi,

I took 360 test photos today. The procedure was:
a) three identical targets (horizontal stripes, large and narrow), one for center focus point, one for extreme right, one for extreme left
b) three sophisticated targets just below each tested targets (to ease sharpness analysis)
c) AF-S, single focus point, VR off, MUP, tripod, cable release, manual defocus before each photo
d) 5 AF photos for each target, then 5 live view photo for each target, thus 30 photos per lens
e) moved tripod to have each lens cover the same area on the targets (i.e. distance = about 50X the focal length)
e) tested
- Nikon 16-35 at f/4
- Nikon 28 at f/1.8 and at f/2.8
- Sigma 50 at f/1.4 and at f/2.8
- Sigma 85 at f/1.4 and at f/2.8
- Nikon 24-120 f/4 at 24mm, 85 mm and 120mm
- Nikon 70-200 f/2.8 VRII at 70mm and 120mm

Results:
- 16-35mm = excellent, no left-AF problem
- 28mm = right and left AF not good, left is worse, same thing for AF and LiveView, same thing for f/1.8 and f/2.8
- 50mm = no left AF problem (but no Liveview)
- 85mm = right and left AF not good, left is worse; LiveView is better than AF (same for AF and LiveView)
- 24-120mm = no left AF problem, AF is very good, LiveView got bad results, same for 24mm, 85mm and 120mm
- 70-200mm = no left AF problem

So, what should I think about these results?

Should I think I have no left-AF problem?

Should I investigate further for potential problems with individual fixed focal length lenses (since zoom have no problems (smaller max aperture))?

I had AF fine-tune active (it was made using Spider LensCal).

Thanks for your help with these mysterious results.

Yvan
Quebec Fine-Art Landscape Photographer
http://yvanbedardphotonature.com

G