it's called homework, and you didn't do it.
Stacking the filters will not help! Either you have a proper filter, or you don't.
Another problem is that the IR light reflected varies based on the vegitation. Deciduous trees and lawn grass reflect the most, and conifers and shrubs vary. Once again, Kodak had the best, and it's never been matched. Your results will vary, and will be useless without the right filter.
Oh, yeah: the tail end (black part) of E6 can be used as an IR filter. I've done it with Kodak, but I never tried it with the others. It might work. If you have some lying around, go ahead and try it, but you may need long exposure times.
Stone, you seem legit, I will send out Monday my 67mm Hoya R72. I can flat rate small box it to your motel/hotel/post ofc or whatnot (shd be $7 w insur) you cover ship to and return with same (flat rate insur). Pm me if you wish. I need it back, no later tan 3/1/13, for when the spring begins here...
This what you looking for (see bottom left)?
Stone, I have had zero issues with the Hoya R72, used it today in 15F, FYI...
I've used a Bower IR72 off ePrey ($47 for a 77mm in 2010) with Rollei IR400 quite successfully. Take an ISO 400 reading, add 6 stops and bracket, bracket, bracket! I agree tests ahead of time are to be highly recommended. Since our eyes don't see IR, we are denied a chance to do a lot of intuitive adjustments.
Most recently I used a Wratten 89B (~695 nm) which was OK, but not quite as good as the 720 nm filter in the infrared effects, and I would expect a 25A to be even less good. I think the more ordinary red filters worked with the old Kodak stuff because it had a very wide sensitivity outside the visible spectrum, a sort of 'area under the curve' biased in that direction.
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
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!
OK, it looks like you bought a 092. That's the correct filter, and it will work fine with all of the current IR films.
Filters cut off at a point, and let in light beyond that.
Films are sensitive up to a point.
So a film is sensitive up to 820nm. A filter at 900nm would be too much (80nm over), but a filter at 720nm would be fine, since it would let in light at 720nm and above.
The B+W 092 is what I use with Konica, Ilford, Efke, and Rollei.
The B+W 091 is what I used with Kodak, since I could still see through a SLR lens.
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