I ran the assessment of my D700 & AF-S 50mm f/1.8 and the calculated AF fine tune is a +6 at aperture f/1.8. I ran the aperture optimization and it calculated a value of f/4/4 as the optimum, but looking at the data, I'm leaning toward f/3.5.For my D700 and AF-S 300mm f/2.8, the calculated AF Fine Tune Value is -15, and the same camera with an AF-S 85mm is +3. For the D7100 the AFFTVs are -1 for the 50mm, +8 for the 85mm, and -8 for the 300mm.Distances to the target were ~1 m for the 50mm, ~1.5 m for the 85mm, ~.7 m for the 105mm (macro) and ~10 m for the 300mm. Neither exact nor exactly what is recommended for the tests, but that's what I've got.I want to go back and run the tests at the optimal apertures for the lenses, as well as testing the lenses with my TC-14 and TC-20 at the optimum apertures: at the largest apertures, addition the teleconverters really degraded the images, but that really doesn't surprise me.Were I you, I'd run the same test again, along with the aperture optimization test and the autofocus consistency test. If you don't get different results then, I'd run a fully manual test, with the step of completely defocusing the camera before every shot is taken and saved for import into the FoCal manual testing process. If that doesn't change the results, you have to decide whether you are happy with the results at the AFFTV of -18 or not. If you aren't, your option is to send the camera and lens back to Nikon. I'm not sure that will result in what you are looking for here, though.