using neutral density filters with IR film.

[Rolland Rainbow Elliott <X93ELLIOTT1@xxxxxxxxx>]

In Theresa Airey's Book "Creative Printmaking" she states:
"Neutral Density filters don't change the tones in an [IR] negative; they
merely reduce the light entering the lens so that a longer shutter speed is
required to record the subject.  Of course, the use of an ND filter will also
permit you to use a large aperature, such as f/2.8 or f/2 for a controleld
focus background."

I thought I read on this list a post (I think by WJ) that stated that neutral
density filters were transparent to infrared radiation.
I've always assumed this to be true, especially after recording a picture of
my friend wearing dark sunglasses with a camcorder fitted with an 87C IR
filter.  My friends sunglasses looked like regular eyeglasses with 
clear lenses.  
If this neutral density filters are trans parent to IR light then
they would not effect the IR light passing through them, but would impact the
visible light through them.  This suggests that neutral density filters do in
fact change the tones in an IR negative because they would reduce the amount
of visible red light passing through without effecting the infrared light
passing through the filter.  

This is just all speculation though.  Has anyone used neutral density filters
with IR films.  And if so what were the results?

Take care Rolland R. Elliott


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