Jean-Claude Berger - Consultant, Formateur indépendant - MCSE - MCT - MCP
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This lens is completely unusual with only two elements instead of 7 for the Nikkor 400/5.6 IF-ED for example. There are two main benefits to this construction. First, the lens is incredibly light (hear easy to use) for a 400mm and the T aperture is better than other lenses. That means that this f/6.3 Telyt should transmit as much light as another more classical f/5.6 lens. But there is a big disadvantage: two elements are not enough to correct the curvature of field. So the Telyt suffers from a solid reputation to present bad results outside a 6mm circle from the centre. Let's see:
This picture was taken with the Telyt at f/8 (the best f-stop overall) on Kodak E100VS film by a sunny day:
Contrast is good, colors are saturated, a little bit warm.
Here is the center portion (leftmost red square) at 4000 dpi:
Though not exceptional, definition is good.
And now the edge (rightmost square):
Details are fuzzy and yes, this is a bad quality picture.
But, one more time, a lens is more than figures or test results. Actually, the image degradation is very linear and when you look at the whole picture, you don't perceive such a difference. For example at half distance between the two squares, image is still good.
In conclusion, one can easily understand why most of this Telyt owners are happy with it. It's a cheap, small, light, fast to use lens and the image center is really good. With most subjects, pictures will be more than sharp enough in the center and for action/nature subjects this lens will be suitable. For more quality demanding work, like landscape, the lack of sharpness on the edge should convince the photographer to purchase a classical (telephoto) lens.
© Jean-Claude Berger, 2003