Test shots of the 300/2.8 AFS-II lens with TC14E-II, TC17E-II and TC20E-II

I included wide open and 6 1/3 stop increments of aperture bracketing. I shot these images in order to determine the best minimum working aperture. Also included F/8 and F/11 shots. Shot from different distances to provide roughly equal subject size (ran out of room when I shot the TC20).

Equipment: Gitzo G1410 + Markins M20 + D200

Shot with a 5-8s Mirror Up delay. Raw images were converted to TIF in Capture NX V1.2 for the cut and paste work. Final image saved as a 100% crop with maximum JPG quality in PS CS.

The images may seem a bit dark; I prefer them this way. Otherwise it is easy to blow the background and some of the blur lines. I think this is easier to analyze. You can download and tweak to suit.

I have shot this glass for almost 3 years now, with many real world images in the gallery here and above, plus my Chincoteague and other wildlife galleries. I think these charts reasonably illustrate the IQ of the various combinations, although I think the TC14 and maybe TC17 look better than suggested here in my real life images.

My assessment of the TC's have always been that the TC14 is very useable wide open, the TC17 a little less so, and the TC20 is dreadful wide open. The TC20 benefits tremendously by stopping down a full stop to F/8. I shoot the TC14 down at least 2/3 stop when I can, prefereably 1 stop, and the TC17 usually down a full stop, but I will shoot the two less powerful TCs wide open if I have to. In real life, ultimate sharpness is the least of your problems, especially for birds in flight. I think these images more or less agree with that assessment.