</span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (OleTj @ Mar 31 2003, 10:12 PM)</td></tr><tr><td id='QUOTE'>Then came the "anastigmat": Two lens elements, one positive, one negative, cemented (usually) together.

The "double anastigmat" is, with a few variations, the basis for all modern lenses. This consists of two anastigmats with a bit of space (and an aperture) between. The convex sides of both groups face out (from the aperture).

The Tessar is a double anastigmat with the rear anastigmat uncemented - 4 elements in 3 groups.
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You really set the brain to working on this one, Ole.

I had workd for many moons in a company whose main product was "advanced optical systems", and that message brought back many memories.
I cracked the books, manly to refresh my memory - and ...

The *first* "camera" lenses - actually in use on the "camera obscura", were simple single-element meniscus lenses ... later to be called "landscape" design. Later, Chevalier designed the "Achromatic Landscape", by cementing another element to it, in 1821 - named for the fact that it corrected a lot of the chromatic abberations of the original "landscape" design.

The "anastigmat" design (remember that astigmatism - where lines that are supposed to be straight - aren&#39;t, therefore; "a"(n)+"astigmatism") does not appear to be a separate design in itself: the first reference I have to it is in the description of the "Protar" and "Double Protar" - designed in 1891 and 1895 by Rudolph, and the "Dagor" by Van Hoegh in 1892. These were all made possible by advancements in glasses - mainly by Abbe and Schott.

A "double achromat - with the rear two elements air spaced", would described the "Petzval" portrait lens of 1841. The Tessar is an assymetrical four-element design, with only the rear two elements cemented together - designed by Rudolph and Wandersleb, in 1902.


How does one tell how the photograph will look when taken with the various lenses? I really do not have a clue. I will go along with Aggies description - the "Little Genie" idea. For all intents and purposes, this WORKS.
I&#39;ve heard long deep, incomprehensible discussions; "The *fool* took this photograph with a Tessar lens ... everyone KNOWS he should have used a Dagor...."
Uh-huh. Right. I&#39;ll file those conversations with all the others in the "Everyone Knows" file. Someday ... I&#39;d love to set up a really valid experiment - taking various photographs with equivalent lenses - although that would not be an easy task. Other than the obvious differences due to focal length, I wonder how many photographers would be able to distiinguish the difference between the Zeiss Planar and the Sonnar - or Distagon - from prints produced with the Hasselblad?

Would be interesting ... but until I become one of the "idle rich" - I have other things to do.

My point, through all this, is that I don&#39;t think the modern lens design matters much.