Quote Originally Posted by StoneNYC View Post
[COLOR=#333333]So apparently the above poster was slightly right, I didn't do my FULL research, I didn't realize there were different transmission rates of the filters
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I'm looking at the different filters on B&H's website.

The question is, if the film is sensitive to 720nm vs higher rated film at 850nm ... and one filter allows transmission beginning at the 700nm's mark where another only starts at 800 or 900nm ... will the film that BEGINS senisitivity at 720nm not pick up the higher rated filter's specturm at all, or will it just take longer to burn in since the IR sensitivity is higher up? so if I wanted even more contrast, I would choose the one that starts at 800 or 900 and expose for longer correct?
Don't do it! A 760 nm filter on the Rollei stuff needs about 12 or 13 stops additional exposure. Bigger numbers are farther into IR, the film sensitivity is already rolling off at 720 and drops like a rock beyond that. And to your question about my statement above, guess I would have been clearer had I said increase exposure by 6 stops. You could set your meter to a lower ISO. I was using a Digisix that only goes down to 6 -- and if I used the 760 filter, I need about 0.25!