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  1. #21

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    Quote Originally Posted by Michael R 1974 View Post
    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.
    Michael, I got out my old 1965 Kodak Pub B-3 on Wratten filters and found the spectral-transmittance curve for the Magenta #32 (aka Minus Green). It transmits blue and only a miniscule trace of green, but it also transmits a good bit of orange-to-red starting at ~610nm. So the filter technology has long existed to make such a filter, and although Ilford's #5 is likely proprietary, it could be very similar to the #32 in order to get the blue/green mix they want. But they might have to live with the bit of orange that comes with it. You see the orange, but the paper is blind to it.

    Just a thought.

  2. #22
    cliveh's Avatar
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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?

    “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

  3. #23
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    Quote Originally Posted by cliveh View Post
    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?
    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.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  4. #24
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    Quote Originally Posted by MattKing View Post
    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.
    Matt, not quite sure what you mean by typical (mudying the water here)? Have you done a practical test of blue v 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

  5. #25
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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.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  6. #26

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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.

  7. #27

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    Matt - it's super simple to pass blue without green. You just need a blue tricolor separation filter like
    a 47 or 47B. Zero green gets through. Or you could hypothetically use the blue output on an additive
    colorhead, though not many of us own those kind of rigs. The only logistical problem with a deep blue
    separation filter would be due to having a hard time seeing the projected image when doing complex
    dodging and burning under the blue light. I don't personally have this problem because even my cold
    light is quite powerful. I have a 14x14 V54 Aristo which uses a single tube of blue-green, so works
    wonderfully for split printing. Without any filtration, it lands VC paper around grade 3.

  8. #28

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    Quote Originally Posted by cliveh View Post
    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?
    VC paper is sensitive to blue and green light. Blue gives high contrast. Green gives low contrast. To get the highest contrast, expose the paper to blue light only. So:

    1) If you have a narrow blue light source (that has no green in it), the answer is to use blue light.

    2) If you are filtering white light with filters, magenta is the answer, because magenta filters out the green and allows blue light to pass.

    This is the simplest way to think about it. In reality paper sensitivities are not "sharp cutting" so there are subtelties. But not anything to really worry about.

    Let me know if this makes sense or if it is still confusing.
    Last edited by Michael R 1974; 03-01-2013 at 07:58 AM. Click to view previous post history. Reason: typo

  9. #29

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    You need to expose with more blue light to get more contrast with modern VC papers. The magenta filters pass both blue and red light. The paper is not sensitive to the red, but your eyes are, so the magenta filter makes the image easier to see. In a like manner, you need to expose with less blue light to reduce contrast. The yellow filters block some of the blue light and passes red and green. The green sensitive emulsion in the paper receives proportionally more exposure. The yellow filter allows you to see the image better.

    For maximum contrast you can use a sharp cutting blue filter like Wrattan #47. You will have a very hard time seeing the image through this filter, but it usually gives a bit more contrast than the Multigrade #5. Blue filters designed for color work, like the 80B or the 82 series, pass all wavelengths. While they do increase contrast with VC papers, they are mot as effective as the Multigrade or Polycontrast filters.

  10. #30

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    Quote Originally Posted by nworth View Post
    ... The magenta filters pass both blue and red light. The paper is not sensitive to the red, but your eyes are, so the magenta filter makes the image easier to see...
    Heck, I have a hard enough time seeing the image to focus with all the magenta dialed in on my dichro head or using the #5 filter. If using a tri-color blue filter is worse, I'll just stick with magenta

    Need more contrast? Change print developer, bleach back the print a bit after printing heavier, bleach-redevelop the neg, etc. (including developing more the next time). I don't think we should be using max contrast on VC papers that much anyway...

    Best,

    Doremus

    www.DoremusScudder.com

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