Re: Apo stuff

[Helmut Faugel TE <htf@xxxxxxxxxx>]

On Mon, 28 Jul 1997, Willem-Jan Markerink wrote:

> Sorry, you are wrong. The UV-Nikkor is in the same league, and there
> have been two older Asahi Ultra-Achromatic-Takumars as well (the
> 85/4.5 corrected from 220nm to 1000nm, the 300/5.6 from 400nm to
> 850nm). I believe Ken Sinclair has one of these beasts (Ken?).
> There has also been a Hassy UV-Sonnar 105/4.3, corrected for both UV 
> and IR (no data given in my books).

My Tokina 3.5/17 for Minolta MD does have the IR-mark between
the focus mark and the DOF mark for f/3.5, but I'm shure it
was not the basic concept to build a IR-corrected lens. AFAIK
the IR mark shows the focus shift around 780 to 800 nm.


> > Other lenses
> > (including Leica's apo lenses, are very well corrected, but not necessarily
> > in the IR. 
> 
> But this fact is even confirmed in the BAS reports!....8-))

Don't trust BAS! The test he makes are real crap! Take a look at the
test in the late 80's and compair them to the new one ... in the 80's
his diagramms showed much more info. And the test he does is only a
MTF-test at 20 lines/mm, where ColorFoto measure at 5, 10, 20 and 40
lines/mm. If a lens is has a bad contrast (low frequencies) behavior
it can perform quite good at medium frequencies (eg. 20 lines/mm) but 
you will get poor results.  

> > If you put an 87a filter over the lens, and load up with an
> > appropriate emulsion, you will have to refocus virtually every lens made
> > for general photographic use, including the Superachromat, as 1000nm is
> > beyond its correction. 
> 
> My literature shows correction from 400nm to 1000nm....

This is also the only lens I know which does not require any focus 
shift for the far photographic IR (> 900 nm). I read an article about
Mr. Bertele's (one of the famous lens designers at Carl-Zeiss, he in-
vented the Sonnar) lens designs an the improvments made on his designs
the Carl-Zeiss Superachromat 250/5,6 was also mentioned. The first
lenses where used in 1973 at the Skylab missions with IR-Ektachrome
film.
 
> > As for 1200nm sensitized emulsions,

I have never read that such emulsions are used for pictorial applications.
These emulsions were mainly used for spectrographic purposes,
and are *history* because this range is covered by semiconductor sensors 
today.


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Helmut FAUGEL                       |  I hate getting junk mails ...
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