Sheet film use

["Lehman John A." <ffjal@xxxxxxxxxxxxxxxxx>]

MartyF2938@xxxxxxx wrote:

> I'm moving up to large format work (4X5) primarily so that I can use
> infra-red sheet film. Can anyone give me some pointers or pitfalls to
> look out for.  I know many of these topics have been discussed in the
> past, such as proper film holders, but I never really paid attention.
...

In theory, holders with five raised dots on the white side are IR-proof,
while those with fewer are not.  In practice, this applies only to
pre-WWII holders; any modern holders should be OK.  Since the sensitivity
of modern high speed IR is about ten times that of the older Kodak IR
which was in use into the 1970's, you have to be careful about leakage.
The main problem is that the felt light traps for the dark slides can let
in IR light leaks.  The trick is to keep the top of the holder shaded (or
best, covered with the dark cloth) from the time you pull the dark slide
to the time you reinsert it.  It is also a good idea to keep the holders
out of the sun.

Bellows on some older cameras are not IR-proof.  Graphics cameras have
been safe for IR since the 1930's at least (as evidenced by Weegee's work,
which also shows the "see-thru" effect on clothing).

IR sheet film is on much thinner stock than regular sheet film, has a
tendency to curl, and is a royal pain to handle in the darkroom.  Loading
and unloading holders is no problem, but tray development is difficult.  I
use a 2500-series Jobo sheet film tank for imersion processing.  The IR
sheet film is a pain to load compared with the thicker regular sheet film,
but once it is loaded, processing is as easy as 35mm.

If you use older lenses, earlier editions of _Graflex-Graphics
Photography_ published tables of IR focus compensation distances for
Optars, Raptars, and Ektars in the normal press sizes (65mm to 250mm).  If
you are using any of these lenses, Email me and I will dig out the chart;
the distances often differ quite a bit from the "standard" formula, and
with LF, you don't have as much depth of field to compensate.  That said,
I usually just focus thru a red filter with a loupe.

Oh yes, the other issue is that the artistic advantages of coarse grain on
your prints disappears :-)

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