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12-21-2011, 11:25 PM   #1
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645N Internal IR?

I'm setting up to (hopefully) shoot some IR film, and I'm hoping that someone might be able to help me here, or point me to a thread or webpage that I simply haven't found...

Question: What internal infrared light exists in the 645N? Will any present affect IR film?

After searching off and on for a few days, I finally called Pentax to simply ask whether or not there were any internal IR sources in the camera...frame counter, data imprinting, etc. I think they were taken aback by a question about a film camera. Now, I didn't get a conclusive answer, but I did learn the following:

- The 645N uses "some internal infrared" but they didn't know the actual wavelength, or really even where it came from.
- Pentax doesn't test with IR film, so they aren't sure if any IR light will affect IR film, or not.
- The 75mm f2.8 lens has an IR focus shift mark, which may or may not be a holdover from earlier lenses...i.e. it may never have been officially tested with infrared, since Pentax doesn't test with IR film. Arg!

I've also heard that the frame counter is NOT infrared, and that the data imprinting is not a factor with films in the 750nm range. I'm planning to shoot 820nm film, and I haven't seen much information on that in the 645N. I know the safe thing to do is to step back to a totally manual camera, but I really want to use the bigger format.

Any help is much appreciated. I suppose if nothing else, I can waste a few dollars.

12-22-2011, 12:09 AM   #2
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I doubt that anything in there would affect your photos, so I'd go for it and shoot some pics By the way, does the 645N have data imprinting? I thought that was only the NII.

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12-22-2011, 05:40 AM   #3
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I kind of doubt it, too, but I don't want to be unsure at $10 per roll, or so. I'm having trouble finding a graph for the film I want to use, also, but I know it has narrow bands of sensitivity, so hopefully any IR would be over the top limit of the film's response.

Yes, it has a data imprint on the bottom edge of the negative. Frame number, shutter speed, aperture, exposure compensation and focal length, I believe. A nice little line of numbers. I know the NII adds mirror lockup and a couple of other things, but the data imprinting came about on the N (one of the reasons I got it over the NII actually).

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