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Thread: Filter factor

  1. #1

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    Filter factor

    I have just found my old Cokin IR filter with a gel type filter that I last used eons ago. It is one of the opaque type and I cannot remember what filter factor I used when it was last used. I have one cassette of Ilford SFX in the fridge about a month out of date and a few rolls of Rollie 400 IR which are about a year out of date so I would like to use them before they get any older.

    I seem to remember I gave it 4 extra stops than the meter suggested is that about right?

  2. #2
    markbarendt's Avatar
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    Mark Barendt, Ignacio, CO

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  3. #3

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    For IR it isn't quite that simple as there may be more or less IR radiation, independent of what your visible-light meter is telling you. There should be guidelines with the film I suppose? In any event, make brackets of a couple of stops.

  4. #4
    Maris's Avatar
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    For Ilford SFX200 behind a Cokin IR filter I just set EI=6 on my spotmeter, measure the scene directly, transfer the settings to the camera and shoot. I get a high proportion of usable exposures and a few surprises. Infrared is, after all, a bit of a visual lottery.
    Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.

  5. #5

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    If it is a Cokin 007 filter, according to my notes its spectral response should be similar to a Wratten 89B, Hoya R-72 or a B+W 092. As such any recommendations you read for those filters should be close. I can't tell you how to expose using SFX200 specifically, as I only use Efke IR820 film. But the above filter equivalences should be good for making cross-comparisons if you happen to find recommendations for using them with SFX200.



    Jeff



 

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