Infrared lightmeter?

Discussion in 'Exposure Discussion' started by cmo, Aug 4, 2009.

  1. cmo

    cmo Member

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    I admit I am lazy, and I don't like to do a lot of exposure bracketing with costly IR film. Normal lightmeters are useless to determine the amount of infrared light. Are there any lightmeters that can do it?
     
  2. ann

    ann Subscriber

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    i just saw an article about one, but i didn't keep it bookmarked, but i bet google would help
     
  3. archphoto

    archphoto Member

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    Did you ever test if putting the filter in front of your lightmeter works, or at least gives you some idea ???

    Sory, not into IR yet.

    Peter
     
  4. thefizz

    thefizz Subscriber

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  5. steven_e007

    steven_e007 Member

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    I use a fieldmaster laser power meter in my job. You can dial in any wavelength you like from deep infrared to ultraviolet and then measure the intensity falling on the sensor. I was all set to do some experiments with it, my pentax spotmeter and some SFX200, we had a glorious heatwave in Britain for about 8 days, and at that exact moment I put an IR film in the camera the weather turned wet, miserable and overcast and has stayed that way ever since :-(
     
  6. Pinholemaster

    Pinholemaster Member

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    Your light meter is not 100% useless. It will give you a starting point, but yes, you will still have to bracket.
     
  7. BetterSense

    BetterSense Member

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    Does sunny 16 work with IR film? I mean I know that the different absorptions of IR filters and the different spectral sensitivities of the films means that determining exposure is difficult; but does the actual brightness of the light change more than sunny-16?
     
  8. keithwms

    keithwms Member

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    I commented on IR metering very recently but I can't seem to find the thread. Anyway my point was that you'd need to meter through two filters in order to get the most reliable results. One filter would be the IR filter itself, and the other would be a high-wavelength cutoff filter to simulate the limited IR response of the film. Bear in mind that most sensors see way past the ~800nm sensitivity edge of the film and thus see a lot more IR light than your film will actually record.... and thus will recommend exposures that are much too short. So you might say, fine, I'll just add an additional factor on top of what my meters tells me. That won't work robustly because the extra correction factor will literally depend on the weather :wink: and then you're back where you started.

    Now, I do have a a high-wavelength cutoff filter for a digital camera and as I recall it was a specialty order, a bit pricey. I guess I could try it out and report, but I don't have one of these meters at the moment, I bought the cutoff filter for a digital camera for other purposes.

    Sunny 16 kinda/sorta works for IR, if you shoot in clear skies and if you have a good guesstimate of the filter factor. But if you have any atmospheric scattering e.g. smog or humidity then all bets are off. So... it works for a limited set of conditions.
     
    Last edited by a moderator: Aug 5, 2009