I have been exploring the limitations of my Tenax II cameras. Here are some results.
My local friendly machinist made me adapter that allows me to mount most Nikkor telephoto lenses (at least the manual focus ones) and a modified 28mm Auto Nikkor and give infinity focus.
I started with the 28mm Nikkor because at the time I did not have a 2.7cm f4.5 Orthometar, and I figured that the 28mm Nikkor might be close enough. I had to modify the Nikkor slightly by grinding off the back flange designed to protect the rear element. Does not affect performance.
The 2.7cm Orthometar that I now have is quite sharp and renders details nicely, but the results consistently have a contrast-blocking haze, Not sure of the cause since the lens glass looks clear, but it is there. The 28mm Nikkor, on the other hand, has contrast and gives excellent results. It is almost impossible to tell the difference in the coverage of a the 28 versus 27mm.
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| 2.7cm f4.5 Orthometar. |
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| 28mm f3.5 Auto-Nikkor-H |
The normal 4cm Sonnar gives nice results with vivid colors and good contrast as well as excellent details. The lens is coated and I am sure that contributes. I really love this lens.
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| 4cm f2 Sonnar. Nice results. |
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| 7.5cm f4 Sonnar. I slightly missed the focus. |
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| 7.5cm f4 Sonnar at f8. |
The 7.5cm Sonnar was the Tenax’s only telephoto. Its results appear to be midway between the 4cm and the 2.7cm. It is sharp with moderate contrast. Not as good as a modern lens, but adequate.
Next we tried the 85mm f1.8 Auto Nikkor. Multicoated and a modern optic. With no focusing aid, a bit of a challenge. Here is where the limitations of a behind-the-lens leaf shutter start to have an effect. Despite the Tenax’s use of a large-opening medium format shutter, vignetting soon rears its ugly head. From wide-open to f4, no vignetting is apparent. By f8, it is obvious, although not a disaster.
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| 85mm f1.8 Auto Nikkor PC, stopped down. Note vignetting. |
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| 85mm f1.8 Auto Nikkor-PC at f4. Almost no vignetting. |
Next we tried the 105mm f2.5 Auto Nikkor. This is the earlier, Sonnar-based version. With this lens, vignetting shows up immediately, although it not a major issue until I stop down several stops. Seems to have a hot spot in the center.
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| 105mm f2.5 Auto-Nikkor-P at f4. |
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| 105mm f2.5 Auto-Nikkor-P at f8. |
Lastly, we show the results with a 200mm Auto Nikkor. Talk about shooting down a barrel!
So, was Hubert Nerwin wise to stop at 75mm? Given the resources he had to work at the time, and the pressure he must have felt from Küppenbender NOT to design a camera that might outshine the Contax, the answer is probably yes, But experimenting with a 130mm Color-Solinear designed for Agfa’s Ambi Silette, I note that this lens does not vignette. Its rear element seats well into the throat of an Ambi Silette, allowing the light cone it forms to clear the shutter. Too bad that such a design was not available in the 1930s. Too bad that I cannot figure anyway of mounting that lens on a Tenax without destroying the Ambi mount in the process.
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| 200mm f4 Auto-Nikkor-Q. |
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