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Thread: Wratten "A" What is it for

  1. #1

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    Wratten "A" What is it for

    Just found an old glass Wratten filter which is just marked A and "A In-cell" on the box. It is red but, but does it have any special use above the obvious use of a red filter? Wrattens I have seen typically have a number association. Exposure compensation seems to be about 2 stops.
    Last edited by A.J. Dickson; 19-Sep-2008 at 08:53. Reason: miss-spell

  2. #2

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    Re: Wratten "A" What is it for

    The Wratten 25A is a deep red filter with a factor of close to 8. Perhaps that is what you have.

  3. #3

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    Re: Wratten "A" What is it for

    The 'letter' descriptions for filters are a method from long ago, pre-WW2 for sure. Kodak shifted over to the number system when the letter code became inadequate. From the book "Kodak Filters" I find that an 'A' filter does correspond to a Wratten #25, so you have the standard red filter for b/w photography. "In-cell" is a mystery though.

  4. #4

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    Re: Wratten "A" What is it for

    Thanks Mark, that pretty much confirms my assumption but I don't have a 25 to compare. I guess in-cell is another phrase for in-glass. I'll have to go out and try it.

  5. #5

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    Re: Wratten "A" What is it for

    Wratten "A" or "No. 25", as mentioned in "Kodak Filters and pola-screens" from 1946, is one of the three filters for color-separation. The others are "B" or "No. 58" green and "C4" or "No. 49" blue. "In-cell" filters can be used inside process-lenses, often together with a waterhouse-stop.
    Last edited by Peter K; 19-Sep-2008 at 09:41. Reason: spelling

  6. #6

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    Re: Wratten "A" What is it for

    Just to add to this, here are the other old designations and their current Wratten numbers:

    K2: 8 (yellow)
    K3: 9 (deep yellow)
    X1: 11 (yellow-green)
    G: 15 (deep yellow-orange)
    F: 29 (deep red tricolour)
    C5: 47 (deep blue tricolour)
    N: 61 (deep green tricolour)

    There are other letter designations for filters.

    Best,
    Helen

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