Darkroom safe light

Discussion in 'Darkroom Developing and Printing' started by piterengel, Feb 2, 2008.

  1. piterengel

    piterengel Guest

    Hi, I've had a discussion with a friend of mine about darkroom safe
    light.
    Even if on Ilford Multigrade paper box a light brown safelight is
    indicated, in my opinion a red safelight works well too. Or, better,
    red light is "more universal" than light brown one. Is this correct?
    Thanks all
    P.
     
    piterengel, Feb 2, 2008
    #1
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  2. piterengel

    Peter Guest

    Red is very good for blue sensitive materials. How red is a
    question. Many lights that look red are only mostly red and radiate a
    lot of other colors, as well.

    Kodak recommends some simple tests for safelights (you can find them
    by searching the archives in this board). Their tests are suitble for
    any sensitive material and let you evaluate candidate safelights
    (whatever is claimed about them).

    Panchromatic and multigrade paper have other safelight requirements.
    Green is often recommended for panchromatic film or paper. That
    recommendation is accompanied with advice to use it late in the
    development, at low intensity. It is recommended because the eye is
    sensitive to green and panchromatic film is a little less sensitive at
    that wavelength. Multigrade papers vary depending on the
    manufacturer's formula

    Long wave IR and night vision goggles work well when money is no
    object.
     
    Peter, Feb 2, 2008
    #2
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  3. Yes.

    Some people don't like/have trouble seeing with a
    red safelight. There is a theory that contrast is
    harder to judge under a red safelight - I don't think
    this is the case. Colored objects do appear
    'contrastier' under narrow band illumination as they
    turn black if they don't reflect 'in-band' - this
    effect happens at all colors. OC safelights, being
    broader band, allow some color vision.

    Red safelights can be quite a bit brighter than
    OC.
     
    Nicholas O. Lindan, Feb 2, 2008
    #3
  4. This is true with some qualification. Modern variable
    contrast papers are sensitive to green light was well as red
    so a usable safelight should not have much output there. The
    Wratten (Kodak) OC, Ilford 905, and similar filters are
    designed for use with VC paper, however, they do have some
    output in the range the paper is sensitive to so the time
    the paper can be exposed to them without fogging is pretty
    limited. A red safelight, like the Wratten No.2, has less
    output in the green and yellow range so its "safe" for both
    VC paper and orthochromatic film, which generally is
    sensitive into the yellow as well as green. Some VC papers
    recommend a red safelight because they have more extended
    green sensitivity than is typical.
    The qualifications are that no safelight is completely
    safe, that is, all will produce some fogging if the
    sensitive material is exposed to the lamp for too long. The
    other qualification is that the sensitivity of the eye has
    an effect on how bright the safelight must be to be useful.
    The dark adapted eye is most sensitive to bluish-green light
    and has very poor sensitivity to red light. So, for a given
    perceived brightness a greenish amber lamp like the OC will
    be greater than a red light with the same actual brightness.
    Where the safelight has some residual output at the
    wavelengths the paper is sensitive to the lower required
    brightness of the amber light may actually make it "safer".
    Visual acuity is also color dependant and is better under
    green light than red although the acuity of a dark adapted
    eye is inferior to the eye in reasonably bright light. This
    may not be significant for reasons noted below.
    Also, some people just find an amber light to be more
    comfortable to work under. As far as judging prints I find
    that all safelights distort perception to some degree. I
    think this has more to do with brightness than with color
    but probably both have an effect. What one must do is to
    keep notes on the way prints look under the safelight and
    then evaluate them later under white light when they are
    dry. After a while you will get some idea of what
    differences the light makes. Note that there is always a
    difference between a wet and a dry print. For some papers
    and surfaces this can be considerable. Generally, both
    maximum black and contrast are greater for wet prints.
    My point is that since evaluation of a print is going to
    be somewhat misleading under the safelight and while it is
    wet the differences between safelights is not too
    significant, you still have to judge the finished print
    under white light.
    A further note: B&W printing is often described in a way
    that makes it seem that development should be adjusted for
    the individual print. I think a better practice is to
    develop for a fixed time and adjust exposure according to a
    scale established by white light results. While errors in
    print exposure can be to some degree compensated by varying
    the development time, and while development time may have to
    be extended for used developer, the process can be
    controlled as much as film development. Because paper is
    developed to "completion", that is, to obtain the greatest
    black density possible with the paper, the contrast is
    pretty much fixed. While there are all sorts of variable
    contrast developers and development techniques in the
    literature most don't work or have only a very slight
    effect: contrast is pretty much built into the paper.
    Another caviat, all safelights should be tested
    periodically. The filters can fade with time. Both Kodak and
    Ilford have effective procedures for testing on their web
    sites. I think the Kodak data sheet is K-4. The two
    procedures are somewhat different but both accomplish the
    same thing so either will do.
     
    Richard Knoppow, Feb 2, 2008
    #4
  5. piterengel

    gr Guest

    In general photo papers are sensitive to green and blue. Yellow can be
    safe, red is safer. Brown is "who knows".
    gr
     
    gr, Feb 3, 2008
    #5
  6. piterengel

    Guest Guest

    Brown really is Who Knows! It's a strange color. It cannot be 'seen' except
    in contrast with another color of greater luminosity.
     
    Guest, Feb 3, 2008
    #6
  7. I think what is being described as brown is the greenish
    amber color of the Kodak OC or Ilford 907 safelight. Its a
    hard color to describe.
     
    Richard Knoppow, Feb 3, 2008
    #7
  8. I think Brown here is just a description of the
    greenish amber of the Kodak OC or Ilford 907 type safelight.
    It can look brown to some people.
     
    Richard Knoppow, Feb 3, 2008
    #8
  9. piterengel

    dan.c.quinn Guest

    So who want's universal? With the Graded paper I use
    a quite bright easy to see about yellow-ish to orange-ish
    light can be used. Dan
     
    dan.c.quinn, Feb 9, 2008
    #9
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