[Leica] Re: LUG Digest, Vol 33, Issue 554

[lrzeitlin at optonline.net (Lawrence Zeitlin)]

On Jan 11, 2007, at 6:23 PM, Len wrote:

> Thanks. I have the use of it (Telyt 560/f6.8) for the weekend along  
> with a R8 body. I
> still find it hard to believe a simple 2 element lens can be that  
> good.

I have a friend, a professor of optical physics, at the University of  
Rochester who insists that the sharpest long focal lenses have the  
fewest elements. The Telyt lens only covers a field of 3.5 degrees on  
a 35mm frame, 4.5 degrees on an M8 frame. With that narrow a field  
you don't need to worry about all the aberrations that multiple  
elements are required to correct. In fact, if you used a narrow band  
pass filter, a single element lens would be almost ideal. Obviously  
Leitz engineers agreed and the results confirm the theory. We need  
the multiple element ASPH designs because we insist on short focal  
length fast lenses for multicolored subjects at close ranges.

The 42" Yerkes telescope, the biggest refractor telescope in the  
world is a two element achromatic.

Larry Z