filter color for hightest contrast with VC paper

Discussion in 'Enlarging' started by David Lyga, Dec 20, 2012.

  1. David Lyga

    David Lyga Subscriber

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    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. cliveh

    cliveh Subscriber

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    No, it's Magenta.
     
  3. Neal

    Neal Subscriber

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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. DREW WILEY

    DREW WILEY Member

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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.
     
  5. David Lyga

    David Lyga Subscriber

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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
     
  6. Andrew4x5

    Andrew4x5 Member

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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/2006130201152306.pdf.

    Cheers, Andrew
     
  7. DREW WILEY

    DREW WILEY Member

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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. michael_r

    michael_r Subscriber

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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. cliveh

    cliveh Subscriber

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    So when you want to print the highest contrast, are you going to use a Blue or Magenta filter?
     
  10. DREW WILEY

    DREW WILEY Member

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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.
     
  11. DREW WILEY

    DREW WILEY Member

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    Sorry ... I noticed a typo ... my cold light system is accommodated to green and blue tricolor. Didn't
    mean to say red. (I had just responded to an additive COLOR printing question on a completely different forum, where red is also relevant).
     
  12. ic-racer

    ic-racer Member

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    The 'blue' filter you used passes too much yellow to achieve the maximum contrast available from the paper. What is wrong with using the #5 VC filter?
     
  13. michael_r

    michael_r Subscriber

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    IC- the blue filter passes too much green, not yellow.
     
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  15. David Lyga

    David Lyga Subscriber

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    cliveh: the magenta is best for highest contrast because, as others have re-iterated, it stops most of the green. The green (and yellow) LOWERS contrast. The lighter blues let it through. - David Lyga
     
  16. Steve Smith

    Steve Smith Member

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    It's worth a look at Ilford's data sheet for variable contrast papers. They state that all of the emulsions are sensitive to blue and the varying contrast layers have varying amounts of green sensitising dye added.

    http://www.ilfordphoto.com/Webfiles/2010628932591755.pdf

    So a bit more complex than one emulsion sensitive to blue and another sensitive to green.


    Steve.
     
    Last edited by a moderator: Dec 21, 2012
  17. RalphLambrecht

    RalphLambrecht Subscriber

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    drew is spot on, butdon't forget one other variable, and that is light intensity. regardless of color. more light willgive more xposure. even a narrow-band red diode will expose the paper over time and make a poor safelightgiven enough time.
     
  18. ic-racer

    ic-racer Member

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    Of course, thank you.

    Anyway, getting back to the topic on hand I would predict a speed advantage using the Ilford #5 filter. I'm surprised I did not test for speed when comparing the #5 to all my magenta dichroic filters. But if you just look at the #5 you see it is not just a magenta filter. I suspect the #5 has some some unique spectral parameters, but Ilford does not give the specs. I have subsequently given away my Ilford filters so can't test it now.
     
    Last edited by a moderator: Dec 21, 2012
  19. DREW WILEY

    DREW WILEY Member

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    Even among papers offered by Harman the different VC papers have different nuances, which one
    just has to learn by experience. But if one is going to jump into the pool in the first place, it's easiest
    to teach simple Blue versus Green tricolor, or basic Magenta versus Yellow variable filtration. Once
    these basics are understood, then the more complex interactions of the actual paper engineering can
    be fine-tuned, like adjusting the water temperature after you dive in. It's a lot easier to demonstate
    on test strips than it is to explain. No need to make a religion out of any single method.
     
  20. michael_r

    michael_r Subscriber

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    I'd be glad to send you a spare set. You make a very interesting point here. I've wondered why when examining the current Ilford MG filters, the #3 seems to visually appear the most Magenta in colour, and the higher numbers look more orange again.
     
  21. bill@lapetelabs.com

    bill@lapetelabs.com Member

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    Variable contrast paper is essentially two emulsions coated on one paper base. The low contrast emulsion is green sensitive and the high contrast emulsion is blue sensitive (positive filtration). Magenta and yellow are negative filtration. With a VCL aristo head the two tubes are blue and green, green at 100% out put and blue a various percentage of out put controlled by a rheostat to create various contrast grades.
     
  22. cliveh

    cliveh Subscriber

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    So guys a lot of confusing responses here, but lets give a straight answer, is it blue or magenta for highest contrast when using multigrade paper?
     
  23. MattKing

    MattKing Subscriber

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    Blue, if you have a source of light with no inherent green (e.g. a later version Ilford 500 head).

    Magenta, if your light source is more typical.

    Magenta with more typical light source is easy to work with.
     
  24. cliveh

    cliveh Subscriber

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    Matt, not quite sure what you mean by typical (mudying the water here)? Have you done a practical test of blue v magenta?
     
  25. MattKing

    MattKing Subscriber

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    Typical = halogen or incandescent or cold light? bulb.

    Non-typical = blue LED with narrow spectrum filter to remove green - harder to make work.

    The challenge isn't with the paper itself, it is with the systems used to control the light hitting it.

    It is far easier to control green light with a magenta filter then it is to produce blue light that isn't contaminated with green.

    And the excess red light that a magenta filter "transmits" improves visibility, without affecting the print.
     
  26. DREW WILEY

    DREW WILEY Member

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    It would be pretty damn difficult to design any automated system of exposure to predict all the variables. You'd have to settle on a single product, and then just about the time you think you have it
    figured out, they'd probably tweak something in the emulsion. Even with Ilford, you've got different VC
    products with different personalities, plus Kentmere VC products offered by the same corp. It would be
    like trying to write a Zone System computer program for multiple film, developer, and lighting situations. You could spend years fiddling with something that only takes minutes with a simple test
    strip.