| 300mm at 200% |
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300+TC-14E at 143% |
| 300+TC-16A at 125% |
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300+TC-20E at 100% |
Nikon 500/4P
and 300mm f4 AFS
with TC-14E, TC-16A, TC-20E
This test was done to answer two questions.
#1. I have been curious about the merits of using a teleconverter, versus resizing an image taken without the converter. Is the detail gained with the longer focal length, greater than the detail lost by the use of the converter?
#2. In my film days, I often shot with a Nikon F5, 500/4P (manual focus) lens, with the TC-16A autofocus converter. This 1.6x converter adds a limited autofocus feature to manual focus lenses. I found it quite useful. When I changed to digital, my first digital camera was the D70, which can not function with the TC-16A, so I sold that converter. When I later added the D2h camera body, I was again able to use my old friend. Folklore on the internet discussion groups has it that the TC-16A is not optically very good. My previous experience disagreed with that conclusion.
Most tests show crops at 100% pixel size. That's ok when the lenses being compared are the same focal length, but since the point here is to compare different telconverters, we need equivalent subject sizes. The question then becomes, do I up-rez the smaller images (without converters), or down-rez the larger images (with converters)? I have shown it both ways. After seeing the results below, I believe that down-sizing the higher magnification image, is the best way to compare.
All tests were shot with the D2h at 800 ISO. Predictably there is some noise at this ISO, which should be ignored because this is a test of the lens resolving power. All shots were taken with mirror lockup.
500/4P with TC-16A
I first tested the 500/4P with the TC-16A, and without. I have not shown those images here, because the results are similar to the tests with the 300/4 lens, and the 300mm test has more data to view. I could not test the 500/4P with the TC-14E and TC-20E, because those items are not compatible due to differences in the lens mount. (I am aware they can be modified to work, but I do not wish to do so).
I tested with the 500mm lens wide open, because that is typically the way I use it. The TC-16A delivered excellent results, in both center and corner sharpness. The TC-16A is a little known gem. As a result, they are cheap. I bought mine recently for $50.
300/4 AFS with TC-14E, TC-16A, TC-20E
| 300mm at 200% |
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300+TC-14E at 143% |
| 300+TC-16A at 125% |
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300+TC-20E at 100% |
In table #1, the first image shows the poor results expected by looking at 200% pixel enlargement. The 100% image of the 300 by itself is actually quite sharp (see below). Comparing the teleconverters, the 14E is very good, the 16A is almost there, but the resolution with the 20E is noticeably poorer than the other two.
The 20E shots were taken at 1/30 shutter speed. I am now curious if the results were degraded by the poor tripod mount, even though mirror lockup was used. I plan to get the Kirk replacement collar for this lens, and repeat the test in the future.
| 300mm at 100% |
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300+TC-14E at 72% |
| 300+TC-16A at 62.5% |
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300+TC-20E at 50% |
I believe table #2 is a better comparison of the various lens resolving power. My observations are:
- Notice how little difference there is in all the images. These are all a good optical match, if you can eliminate camera shake.
- My second observation is that the TC-14E image may actually look better than the original lens. Technically that's unlikely (maybe impossible), but certainly the TC-14E does not hurt 300/4afs in any way.
- The TC-16A has slightly less contrast than the first two, but resolution is still excellent.
- The TC-20E is definitely a notch down, but still quite useable. At the distance these images were taken, not only could I not see the two vertical lines, I couldn't see the entire spot.