The D800 has increased resolution and has the ability to resolve detail that looks like it needs adjustment on another camera.
There is also the issue of FX vs. DX. A target on the D7000 is zoomed - and effectively has more depth of field. The D800 target would be smaller and have a very shallow depth of field.
There can be errors in either camera. Even with those errors, the cameras might be within spec.
Lighting conditions affect resolution. Choice of WB, light levels, etc. can all have an impact on your fine tuning.
There is variability in AF accuracy. If you focus the same lens and camera combination 5 times, you will get a different answer every time. The variation may be small or large, but there is always variation.
There can be differences in the AF target. That's a test variable, but sometimes certain targets are difficult for specific camera and lens combinations.
Sat 26-Jan-13 01:13 AM | edited Sat 26-Jan-13 01:17 AM by elec164
>Considering that the lens is fine on the D800 suggests that >it is not a lens issue, but rather a body issue. >
There's two articles over at LensRentals that would suggest that this is faulty logic. They sort of coincide and reinforce what Eric posted and suggest that it could be a combination of both the body and lens.
I have a thread in D7000 forum about my recent experience with the 14-24/2.8. I went through a similar issue with a Sigma 24-70/2.8.
Short version: I have to dial in -15 to -20 AF tune for these two lenses on both my D7000 bodies. Yet other lenses are fine: the 70-200/2.8 VR-II is spectacularly sharp with no adjustment, again, on both bodies. A cheap kit lens (18-55) is likewise fine.
My feeling is that as long as you can achieve satisfactory results with the AF tune, just do so, and enjoy your body + lens. I got my Sigma dialed in about a year ago, and have used it since then, and it's performed just fine.
My 28-300 Nikkor was moving from -4 to +3 on D3x, D3s, D700 bodies. It is plain 0 on my D800/s and D4 bodies. My 70-200 looks the same. Go figure. Only one thing is in my mind - Nikon dramatically imroved FT system/auto calibration. Dimitri.
My 50 f/1.4 + D7000 combination is exactly the same. Through trial and error, I settled on -20 AF compensation. I didn't do any controlled tests or anything, just took a whole bunch of photographs under "real world" conditions and ended up concluding that -20 gave me the highest "hit rate" for sharp images.
I'm borderline disappointed with the 50mm (which is fairly new to me). I bought it looking for a razor sharp prime, since I already have that focal length covered by several zooms. As it is, even with the AF adjustment, I can't say it is noticeably sharper than the zooms. The better DOF control from the f/1.4 is nice, though.