Tri-Color Exposures using Color IR film

[Rolland Elliott <rolland_elliott@xxxxxxxxx>]

Has anyone ever tried doing a Tri-Color Exposure with
Kodak's EIR (Color Infrared Film)?

I've seen a few examples of this technique done with
regular film.  With regular film, a camera is set on a
tripod and three multiple exposures are made. One
exposure is with a red filter, the next exposure is
wtih a blue, and the last exposure is made with a
green filter. In theory, you are basically breaking up
white light into the three additive colors, red, blue
and green, and exposing the film to each color with a
time delay.

Because of the time delay things that move with in the
frame become multicolored, typical subjects are moving
clouds and rushing water.

Unfortunately I'm a little rusty with my color theory,
so I was wondering if someone on this list could
validate my approach for doing this with color IR
film.
Since color IR film has three light sensitive
emulsions: one responds to green light, another
responds to red light , and the final one responds to
IR light (in addition they all respond to blue light,
hence the need for a Yellow #12 filter, also known as
a minus blue filter), I propose the following:
1. Compose your subject and mount the camera on a
tripod.
2.  To obtain correct exposure triple your ISO film
speed. Example an ISO of 250 would be an 250x3=
750 ISO.
2. Set your camera to make three multiple exposures:
A.  First exposure is with a Yellow #12, Red #25, & IR
blocking filter.
B.  Second exposure is with a Yellow #12, Green #58, &
IR blocking filter.
C.  Last exposure is with a 87 IR transmission Filter.
A Yellow #12 filter is not necessary because the 87 IR
blocks all visible light.

I actually have all of the above filters, so I'm
thinking of trying this technique in the next few
weeks, as soon as I see some cool cloud formations. 
I'd appreciate any feedback on my proposed technique.

One thing I'll deffinitely do is bracket.  Getting the
correct exposure on one frame of EIR is hard enough,
with three different exposures, it will be pure hell. 
I'm also thinking that I'll use a 87C filter for the
last exposure since I don't think my IR blocking
filter from B+W blocks out all IR light very
effectively. This might help to keep the vegetation
and other highly reflective IR subjects from getting
over exposed.

Sincerely Rolland Elliott
P.S. If the false colors of Color IR film are not
wierd enough for you, this technique should spice up
your shots.




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