Which Flash Meter for Low Light Precision?

Discussion in 'Darkroom Equipment' started by Rafal Lukawiecki, Sep 25, 2012.

  1. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Could anyone recommend a flash meter that would be suitable for evaluating fairly low levels of flash illumination somewhat precisely? I am interested in the range of 0.1-5 lux, with a precision of 0.1 lux. A flat-style (cosine) receptor would be needed. I don't mind if the meter can be used for other applications, but I am not looking to use it for anything other than this purpose. Inexpensive, even if older, would be a plus.

    The main reason for using it would be to check the evenness of illumination while exposing sheet film, by contact, with Stouffer transmission tablets, illuminated by a flash head, as part of my mini-project in make-shift sensitometry. I was not sure if this is the right forum to post this query on, please feel free to move the thread if I erred.
     
  2. Chan Tran

    Chan Tran Member

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    If you check meters from the 3 big meter makers, Gossen, Sekonic and Kenko you will find that about 2.5 lux.sec is about the lowest they can measure. So I don't know.
     
  3. Two23

    Two23 Member

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    I am a night photographer. The only thing I've found that works constantly is to just use my Nikon DSLR to get an exposure and then use those settings on my film camera.



    Kent in SD
     
  4. Chan Tran

    Chan Tran Member

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    I have an idea. As you have found out that the flash is more consistent if it is set for relatively higher power rather than very low power. Perhaps, you could use density filter and meter the flash without the filter and use the filter for the actual exposure? You can set the flash power very high, measure with and without the filter to determine accurately the filter factor. Then dial the flash down to a level that when you put on the filter it would be right for your exposure. Finding very low level flash meter would be difficult.
     
  5. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Chan, I think the filter route is the way to go, if I get nowhere looking for a low-light flash meter. Ideally, based on the other discussion, this would be a more "mechanical" filter (holes etc) than a normal ND, but I'm happy to work with Lee lighting gels in the meantime.

    I wonder if common NDs, placed on a flash head, behave the same as when they are over a lens, in terms of reducing the output of a flash by a known log factor. I will check that at higher power levels with my meter.
     
  6. Bill Burk

    Bill Burk Subscriber

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    They do, but. Wratten No. 96 ND filters are measurably (though not normally significantly) yellow, which can explain differences you found between different brands or kinds of film (the films may have differing spectral sensitivities - the yellowness is significant in this application; sensitometry).

    Using the flash at power settings well-above your planned final setting... through any mechanical filter you create, you can find the difference. Remove the filter and measure... (Label the "filter" with the effective Density) Reduce the flash and measure again... Replace the filter and go to work testing.