EFKE 820 IR and ROLLEI 400 IR films

During a trip to the UK over Christmas, I took some EFKE and Rollei IR films to try. I was using a filter that filters light up to 720nm and it worked fine for the Rollei 400 IR film when rated at ISO 6. When using it with the EFKE film, it did not work that well at all. I saw that many people rate the EFKE film at ISO 25 with filter. I kept mine at ISO 6. Both films were souped in Rodinal 1:50 and only the Rollei actually had printable images on it. Films were souped for 12 minutes. The Efke film appeared to be way under exposed with hardly a trace of a recorded image. I'm not sure what went wrong considering I had heard these films need generous exposure when filtered.

I also thought that maybe I needed a higher wavelength IR filter with the Efke?? Anyone have any ideas?

My 89B filter cuts about 6 stops so 6 stops from ISO 100 would be ISO 1.5. It works for me. Here is an example...
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Andrew,

I use the Efke IR820 with an 88b (700nm cutoff) or 88a (770nm cutoff). It's very slow, more like 1 ISO for me with filter. My meter of course doesn't give many shutter speed/aperture combinations at this low speed so what I do is set my meter for ISO 50 (an arbitrary number), then meter the scene (not through the filter) paying special attention to shadows, which you might want to place around zone 4. Then open up 6 stops (->25->12->6->3->1.5->.75) from the indicated setting and you should have a reasonable exposure. Bracket a stop either side of that and you'll have a selection to choose from. Meter readings are only approximate because the IR wavelength is what's important but this seems to work reasonably well for me so far.

Mark

I haven't found a need to rate this film *quite* as low as some others with an 89b filter, but I've converged on about EI 6 or 8, 12 at the outside. I have had decent luck metering through the filter, but the sample size is small enough that maybe it is no more than luck.

But remember that the catch with IR is that you can't see how much of it there is! If there's a lot of visible light, but it's skewed towards the blue end of the spectrum, things can look pretty bright to the eye but very, very dark to the film. I think everyone needs to do some fiddling with this film in the light conditions in which they plan to shoot.

To me it sounds like you don't need to change the filter, you just need to rate the film a lot slower.

-NT

Last summer I bracketted a roll of 120 Efke 820ir and used a Lee 87 filter (740mm, I think), under typical sunny 16 conditions. I had to go two stops over ISO 1, that is ISO 0.25, to get a decent negative. So rate low and go lower!

Searching for scanned print....
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This was sort of set up to give me lots and different highlights and shadows.