On Mon, Sep 25, 2000 at 12:30:04AM +0000, John A. Lind wrote:
> I think it's a matter of who made the lens, it's specific formulation, and
> it's condition. My 45 year old CZ 50/1.5 Sonnar (on an equally ancient ZI
> Contax) does a superb job with color. I can't detect any chromatic
> aberration projected to 35" X 50."
Cromatic abberation is not the point. A b/w-lens with serious cromatic
aberation
would be unsharp. I heard of other reasons why the earlier Summicron lenses
for the Leica should be better for b/w whereas the newer is more a color lens.
But I can`t remember the given reason.
Some of the Leicaphiles would probably
> weigh in with similar observations about the Leitz glass on their postwar
> LTM's or early M2/M3's. I don't see any noticeable color shift in it
> either. Variations in color temperature when various chromes was shot have
> a greater affect on the color balance.
>
> Admittedly, that's anecdotal with a sample of *one.* Even older pre-war
> lenses were uncoated, so I think a comparison to them would be inherently
> unfair. Postwar lenses were single-coated up to some time in the 1960's
> when high end lenses started appearing with multi-coating. That might make
> a difference with some, but not all lenses, because the older ones
> typically had one or two fewer groups, and some have thinner glass elements.
>
> [Historical note: CZ started coating camera lenses some time around
> 1941/1942 during the war; CZ developed the first practical coating method
> in the 1930's but it was held as a state secret.]
>
> It's also dependent on the glass used in the lens formulation.
> Multi-coatings add very little to light transmission through high index
> glass. A good single coating (Magnesium Flouride??) on high index glass is
> very broad-banded. In general, the higher the index, the more broad-banded
> a well designed single-coating becomes, and the additional transmission a
> multi-coating can provide becomes less (the purpose of MC is to make the
> coating effect broad-banded).
>
> That 50/1.5 CZ Sonnar is my *best* lens, followed very closely by the
> multi-coated 50/1.2 Zuiko.
This is interesting to hear, especially after reading:
http://www.photodo.com/art/When3.shtml
It remembers me my prof showing us a table with lot`s of rows of numbers how
engineers calculated
lenses before computers took over. But he was enthusiastic about their
understandig of lens construction. He told that he tried to improve some of
this `old` designs with computer programs, and he realized that it was
unpossible to do so until an additional lens element or newly available glass
was added.
Frieder Faig
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