Wratten 25 vs. Wratten 29

[boblong@xxxxxxxxxxx (Robert Long)]

Walter Clark, writing about the original Kodak 35mm IR emulsion, says
that there is no practical difference between these two filters
because that emulsion is insensitive to the red range in which there
is a difference between the filters.  His wedge spectrogram does show
diminishing sensitivity through the red range before dropping off
altogether in the yellow-greens.  I've never seen a wedge spectrogram
for HIE.  Does it behave the same way?

What I'm really asking is, after having gone to considerable trouble
to find a Wratten 29, does it really do nothing for me that my old
Wratten 25s don't?

Bob Long
(boblong@xxxxxxxxxxx)

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Topic No. 10