Fiddling with odd filters for EIR

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

Dear gang,

I recently obtained a Kodak Filter handbook for technical and 
scientific use. The transmission plots triggered some thoughts about 
alternative filter use with Ektachrome IR

If speed isn't a problem, one could use odd Wratten filters like 99, 93, 74, 75,
61 and 58, with a partial transmission between 400-500 and 600nm,
and a total transmission beyond 700nm....this means that red is
mostly blocked, IR not. And by holding back the rest of the visible
spectrum, real IR should be more pronounced, but not as with a dark IR filter
(rendering only red tones).
One can also pick the most blueish one of the above, and combine it
with a range of #8, #12 and #16, the latter to influence only the
visible part, but still with a block of 600-700nm.

But it most likely kills your film speed by several stops....the
visible part is reduced to 50% of normal (compared to a #12), and
you totally block 600-700nm, where EIR is quite sensitive.

Btw, most of the above colors are referred to as some kind of 
green....tri-color green, monochromat green, etc.

Any comments?
I know one of our members experimented with the old EI and a green
filter, but only with a standard b&w green filter I believe.


- -- 
Bye,

Willem-Jan Markerink


      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]
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