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  1. #1
    David Lyga's Avatar
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    filter color for hightest contrast with VC paper

    The other day I tried exposing VC paper using a circular blue camera filter (the one for exposing color film under tungsten), instead of the standard VC filter, and found out that using the highest grade magenta filter (intended for VC printing) gave slightly more contrast. I thought that 'blue' was the color needed for the highest contrast. Comments? - David Lyga

  2. #2
    cliveh's Avatar
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    No, it's Magenta.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

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    Hello David,

    A long time ago I found the same thing when using a blue dichroic filter. After looking more closely at the transmission curves I came to the conclusion that the magenta (Polymax #5) filter I had blocked more of the green than the blue filter. Then I bought a color head and only bring out the #5 on grand occasions.<g>

    Neal Wydra

  4. #4

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    The high-contrast layer is blue sensitive, so the correct answer is blue. What magenta does is filter
    out the complement low-contrast color (green), so that only the blue gets to the blue component of white light. Some red light gets thru too, but the VC emulsion is blind to this. This is just basic color theory, i.e., additive versus subtractive. But given the fact that primary blue filters are quite dense,
    it is generally easier in practice to work with subtractive magenta. I use both methods, and identical
    results can be achieved. But if you do additive split printing, you need a blue tricolor like a 47,
    not just a light blue tungsten-balancing filter, which will still allow a considerable amt of geen thru.

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    David Lyga's Avatar
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    Ah, so that is the answer. Thank you Drew. The green gets by with the blue filter and needs to be stopped. That gives me my answer because, at least theoretically, and as Drew re-stated, the highest contrast demands blue. - David Lyga

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    According to Ilford, blue light will give you maximum contrast (as described in the link).

    However, the filter you are using won't completely block out green light because it is, after all, a color correcting filter. Presumably, a blue tri-color filter would give maximum contrast.

    http://www.ilfordphoto.com/Webfiles/...0201152306.pdf.

    Cheers, Andrew

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    What you do to see how the paper sees, is to take some bright green object and view it thru your
    chosen filter material. A blue tricolor will block all green - hence the green object will appear completely black. But papers are typically a little more complex than this in real use, and with some
    you might not be able to achieve DMax (maximum density) without at least some token exposure
    of the green layer too. Hence you might get maxiumum contrast, but it still won't look "contrasty"
    because you won't achieve a deep black. Not all VC papers are the same in this respect.

  8. #8

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    Questions like this seem to come up fairly often. I strongly suggest anyone interested in black and white photography and printing (in colour work this would go without saying) commit a basic additive/subtractive colour wheel to memory (and/or keep a small copy in the camera bag and/or keep one in the darkroom near the enlarger. It is an invaluable visual aid to anyone not familiar with colour mixing/absorbtion, complements etc. It will help with filters in the field, and will help darkroom workers understand what the various filters (additive or subtractive) are actually doing.

  9. #9
    cliveh's Avatar
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    Quote Originally Posted by David Lyga View Post
    Ah, so that is the answer. Thank you Drew. The green gets by with the blue filter and needs to be stopped. That gives me my answer because, at least theoretically, and as Drew re-stated, the highest contrast demands blue. - David Lyga
    So when you want to print the highest contrast, are you going to use a Blue or Magenta filter?

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  10. #10

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    Time is the critical factor for me, so I'll load up different enlargers ahead of time with different size
    negs I plan to work with. My high-tech color enlargers are generally dedicated to color work, but I
    do have a traditional Omega D with a colorhead, which is handy for 4x5, MF, and 35mm VC printing
    using the subtractive variable YM route. My 8x10 unit, however, is fitted with a blue-green cold light,
    so is ideally controlled using tricolor red and green filtration (split printing). My negs are developed
    with enough consistency to where I often just use unmodified light, or just slightly tweak it with
    green to put more detail in the highlights, or some blue punch for more contrast in the shadows. With
    the Omega colorhead, I often might want a bit more simple contrast using magenta when higher degrees of magnification are needed. The problem with strong blue filters in particular is that you need a very strong light source. Not all enlargers will handle these. But unlike color printing, the needs of VC paper are not nitpicky, and you can get optimized, even identical, results with either additive or subtractive filtration.

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