Part 3: lens resolution tests with my D800

<p>After testing my AF-S 24-120/4G on the D800, I decided to check out my other AF-S lenses with the 1951 USAF resolution charts. Results were better than past film tests, likely due to elimination of flatness issues by using a digital sensor. Lenses tested were the 600/4 AF-S (Version 1), 300/4 AF-S, TC-14E II and the new TC-20E III. Tested were center resolution and corner resolution. Both the 300 and 600 tested at or near 72 lp/mm wide open and at least 64 lp/mm at the corners. Minimal improvement was made by stopping down just 1 stop which improved the corner to 72 lp/mm and also improved contrast a tad. Center resolution was at least as good as when tested wide open. Further stopping down did little to improve things demonstating these are highly corrected optics that are diffraction limited to the corner by about f/5.6. Adding a TC-14E II did little to degrade the resolution on both the 300 and 600 with optimal performance only one stop down giving improvements in contrast and resolution to 72 lp/mm centrally and 64 lp/mm in the corner with the 300 and 64/56 with the 600. The TC-20E III on the 300 faired a little worse than the TC-14E II giving at least 56/50 one stop down at it's optimal setting, wide open being only slightly softer but still excellent. Further stopping down yielded little or no improvement with the 300. On the 600, the TC-20E III was a little soft wide open but stopping down one stop slightly improved things to 44 lp/mm centrally and over 22 lp/mm at the corner. Sagital resolution was much better at the corner but it was meridional performance being the limiting factor in resolution at the corner as expected with Nikon's MTF scores as well as other manufacturers of super teles. Stopping down 2 stops was not much better than 1 stop down and given the effective f/16 openning that makes vibration an issue with a slower shutter speed in all but bright light with an effective 1200 mm lens in FX, I would not stop down any more than 1 to 2 stops at best. As expected with the 600 and TC-20E III, the was a slight amount of color frringing on the corner target. All tests done at ISO between 400-1250 to achieve a high enough shutter speed to suppress vibration. Resoultion was checked at 100%% crop and shot in RAW. I suspect at ISO 100 and if there were no vibration from the shutter or mirror, the results would be better with the TC-20E III on the 600.</p>

<p>Thanks Alan. I have always been happy with the performance of the TC-17e on the 300/4AF-S. and I suspect that were you to test that combination, it would perform more closely to the 300/1.4 combination than the 300/2.0 combinations.</p>

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<p>I agree that the TC-17E would perform between their 1.4x and 2x converters based on what I've read. If the TC-17E utilized all the AF points as flawlessly in any light as the 1.4x converter on an f/4 prime I'd probably sell both and just get the TC-17E. I did re-test the 600 with the TC-20E III and found significant improvement centrally to 54 lp/mm wide open and 60 lp/mm stopped down two stops with ISO 100 and better vibration suppression. Testing mid-frame resolution revealed 33 lp/mm wide open improving to 54 lp/mm stopping two stops down. </p>