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  1. #1

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    Infrared Exposure Meter?

    Is there such a thing as an infrared exposure meter? A narrow-field one would be optimal.

    I'm interested in trying some near-IR film like SFX 200 but want to be able to meter reasonably accurately how much IR of the appropriate wavelength is reflecting off the foliage so I can more accurately expose and develop the film without having to bracket several frames on a minimum of two rolls... this allows me to adjust development on the second roll.

    Hmm... now that I think about it burning extra film is probably more cost-effective than a dedicated IR meter because I won't be shooting that much. None-the-less... my curiosity is up now!!

  2. #2

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    Re: Infrared Exposure Meter?

    Yes
    Here's one:
    http://www.davidromano.com/TrueIRMeter.html

    Bracketing is for sissies.

  3. #3

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    Re: Infrared Exposure Meter?

    Quote Originally Posted by vinny View Post
    Autometer V, with blue filter removed/substituted by a Wratten IR filter. The same stunt can be pulled off with any meter without a IR blocking filter (or with the filter removed) - the real value (above the hardware components) of that kit would be in the accompanying user manual with sensitivity tables, as you'll go through insane amounts of film working out the latter.

    The real issue is that the said IR filters only model the visible/IR transition, and cannot model the spectral response of the film within IR - where the currently available films are distinctly odd and difficult.

  4. #4

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    Re: Infrared Exposure Meter?

    That's pricey but not as bad as I expected. Maybe I can find a used one?

    I'd most likely be using #25 and #29 filters since I'm not looking for "pure" IR but rather extended red... like SFX200... because I want light but not white foliage and I don't want significant halation effects. I'm looking for subtle tonal enhancement rather than dramatic effects. The reason for the IR meter is to provide more predictability.

    I guess the only concern, as mentioned above, is unpredictable exposure readings due to the meter seeing different IR wavelengths than my film and filter. Is there an affordable/predictable way around this if I stick to one film such as SFX200?

    RE modifying a meter myself: Any link(s) to basic instructions?

    Quote Originally Posted by vinny View Post
    Yes
    Here's one:
    http://www.davidromano.com/TrueIRMeter.html

    Bracketing is for sissies.

  5. #5

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    Re: Infrared Exposure Meter?

    Quote Originally Posted by Old-N-Feeble View Post
    That's pricey but not as bad as I expected.
    Well, if that offer still exists and the meter is new (Minolta quit making meters many years ago), that would be less than a hundred above the retail price. The same goes if he now ships the Kenko relabelled current version of the meter (KFM-1100). Not that much, if there are good tables along with it. But apart from these, any meter with a removable (or never installed) blue filter would do just as well for a DIY conversion.

  6. #6

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    Re: Infrared Exposure Meter?

    Quote Originally Posted by Old-N-Feeble View Post
    RE modifying a meter myself: Any link(s) to basic instructions?
    None that I know of - the process itself probably is too trivial, and the more complex calibration issues are exactly the same as for meters without filter modification.

    Given the low IR sensitivity and limited spectral range of the remaining IR films, attaching a deep red or IR filter to a unmodified meter might already be good enough. For EIR or HIE you had to remove the (IR cut-off) blue filter from meters with silicone blue cells (and ideally substitute it with a deeper IR filter), and then could meter through the same filter you'd use for exposure. Mind, these films had a wide IR response and good visible/IR relation. With all current films it never is a 1:1 process, you still have to compensate considerably to match film to meter readings, as their IR sensitivity is odd, short-range, wobbly and disproportionally lower than the visible one - hence it might even be advisable to leave the blue filter on.

  7. #7

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    Re: Infrared Exposure Meter?

    Basically, what you're conveying is, particularly with films with spectral response similar to SFX200, I'm just as well off metering through a #29 filter with a non-SBC meter? There's not much I can do to more accurately read the IR reflected from foliage? If that's true then I'm back to bracketing and shooting a roll of film as a back-up to development time.

    Quote Originally Posted by Sevo View Post
    None that I know of - the process itself probably is too trivial, and the more complex calibration issues are exactly the same as for meters without filter modification.

    Given the low IR sensitivity and limited spectral range of the remaining IR films, attaching a deep red or IR filter to a unmodified meter might already be good enough. For EIR or HIE you had to remove the (IR cut-off) blue filter from meters with silicone blue cells (and ideally substitute it with a deeper IR filter), and then could meter through the same filter you'd use for exposure. Mind, these films had a wide IR response and good visible/IR relation. With all current films it never is a 1:1 process, you still have to compensate considerably to match film to meter readings, as their IR sensitivity is odd, short-range, wobbly and disproportionally lower than the visible one - hence it might even be advisable to leave the blue filter on.

  8. #8

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    Re: Infrared Exposure Meter?

    Quote Originally Posted by Old-N-Feeble View Post
    Basically, what you're conveying is, particularly with films like SFX200, I'm just as well off metering through my non-SBC through a #29 filter? There's not much I can do to more accurately meter the IR from foliage?
    Yep - there is not much to be done about SFX (and other similar speed trap films) that can't be done with a regular meter, they don't reach far enough into IR that you need to bother. And EFKE on the other hand has such a bizarre low-sensitivity IR response that a corresponding metering filter would be quite a expensive research subject. Hacked meters were more helpful in EIR/HIE days.

  9. #9
    Format Omnivore Brian C. Miller's Avatar
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    Re: Infrared Exposure Meter?

    Quote Originally Posted by Old-N-Feeble View Post
    ... because I want light but not white foliage and I don't want significant halation effects. I'm looking for subtle tonal enhancement rather than dramatic effects. ...
    If it isn't Kodak HIE/HIR, then it's always questionable about what you will get. Here's the reason: different plants reflect IR in different ways. The cell structure reliably reflects IR at the wavelengths that made HIE so great as an aerial surveillance film. But without that spectral sensitivity, you don't know what you'll get if it isn't deciduous foliage. Up where I live most of the trees are conifers. These reflect IR in different spectra, and not all reflect IR in the same spectral sensitivity as is needed for the film. Some are black, some are grey, some are white, and that's with a very dark B+W 092 filter. (B+W 091 = Wrattan 29)

    If you use a 25, then you may not get anything. If you use a 29, you might see a bit with deciduous foliage. One time I was out with Konica IR (similar to SFX 200 and Efke), in the deep shade under pines or similar. I thought that there wasn't hardly any IR around. Boy, was I absolutely wrong. The first exposure and +/- brackets were good, and the rest just turned the film oh-so-overexposed.

    With IR, you just take your chances.

    Oh, yeah, halation: you won't see it. Kodak film did not have an antihalation layer. The only film you'll get with this is the Adox (Efke) "Aura" IR film.
    "It's the way to educate your eyes. Stare. Pry, listen, eavesdrop. Die knowing something. You are not here long." - Walker Evans

  10. #10

    Re: Infrared Exposure Meter?

    This site's bandwidth has been exceeded.

    http://www.999-wed.com/pg/pg9-infrared-allenmeter.htm

    But he takes a $20 lux meter and converts it to IR, and shows you how. I would try that before messing up a perfectly good Minolta.

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