Re: ..Russian IR films..

[eml@xxxxxxxxx]

This problem of storage at -19C sounds very like the sort of thing 
one might have to do with a film which can go beyond 1100 nm.  The
longer IR wavelengths, when compared to visible light, when thought 
of in terms of ideal black-body radiation, are not at 5500C like
daylight, nor even like 2600C (small tungsten household lamps,
but more on the order of 300 or 400C.  Think if you will of
dull-red iron at 500C or so.. which is still somewhat visible, though
most of its radiation is in the infrared.  What is the sensitivity
of such long-wavelength IR films to normal comfortable human temperatures?
I have no idea, but I would suspect that these warnings about deep-freezing
and immediate use are not unreasonable exaggeration.

Though I am as interested as anyone in seeing these films be available,
and doubtless will try them, I have a few aditional caveats:

1.  Don't even THINK of using one of these extreme IR film with your
favorite 15 elements-in- 8 groups zoom lenses!  At these wavelengths,
the odds of even the best multicoatings working at all are nil.

2.  Unless the manufacturer has tested and absolutely guarantees their
plastic cameras are opaque to IR in this range, don't even think of
casually dropping a roll in your point&shoot or plastic SLR.  They MAY
be fine, but in this case, METAL is BETTER!  Same goes, possibly, for
certain cloth focal plane shutter curtains.

3.  Expect NO worthwhile correction for chromatic aberration, coma,
etc, from any complex lenses.  You're so far outside the design range
at 1100 to 1200 nm, that a simple triplet or doublet might well 
perform as well as a complex, fast modern optic.  (Mirror lenses, 
for obvious reasons, excepted.)

The range up to maybe 900 nm is fairly close enough to visible light, 
and with IR films normally available, the lens designer may well have 
extended the width of his design's corrections to do a fair job
here.  But the more highly corrected a lens is in its bandpass, 
usually, the quicker its corrections go wacky OUTSIDE that range.
1200nm is 70% longer in wavelength than the end of the visible
spectrum.  Konica is sensitive to, at most 15 or 20% beyond that
border.  HIE to maybe 25 to 30% beyond.  At 70%  beyond, the lens designer
never even gave correction the most fleeting thought!  

I am not trying to discourage anyone!  It's just that when handling
materials of this sort, it is likely that a whole bunch of things
that we take granted, from shutter curtains to processing tanks and 
changing bags, and perfectly good lenses that may start acting like
the bottoms of coke bottles, will pose new challenges!  As always,
be prepared to experiment and be prepared to waste film!

My $.02

Ed Lukacs

-- 
    _/_/_/_/ _/_/    _/ _/   | Edward M. Lukacs 
   _/       _/ _/ _/_/ _/    | eml@xxxxxxxxx 
  _/_/_/   _/  _/  _/ _/     | 3850 Tunlaw Road, NW, Apt. 815 
 _/       _/      _/ _/      | Washington, DC 20007
_/_/_/_/ _/      _/ _/_/_/_/ | Telephone: (95) 202-338-1489


------------------------------

Topic No. 18