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Thread: VC Safelight

  1. #11

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    Quote Originally Posted by ath View Post
    Thanks, Ian.
    In your cited post you are talking / citing Agfa regarding the fact, that EVERY safelight will eventually fog paper if it is exposed long enough. This is perfectly clear.
    However, I'm talking about the fact, that RED safelight is safer than orange, green, brown, yellow, PROVIDED the fact, that they have the same intensity.

    A look at the spectral sensitivities makes this perfectly clear.

    These magazine articles you cite, were these scientific articles or "popular photography" type articles?
    In principle, one could design a vc paper with red sensitivity and a sensitivity gap at, let's say, yellow. Thats how colour paper works. But I'm not aware of a current paper like this.
    I was watching intensely, and agree that the article is not "red specific". I have always know this to apply to any filter used. I have been using Fotokemika Varycon paper which suggests the safelight be in the red spectrum. Noting that the paper's spectral sensitivity goes up to 570nm explains why. And for example Fomabrom's spectral sensitivity drops off at 525nm, and they suggest yellow-brown, red or orange is is fine. I switch between using a cheap red party lamp ($2.48 from walmart), an OA, and or a Kodak No. 10. I really should run some tests, but have never experienced any difficulties.
    Last edited by DannL; 02-15-2008 at 02:56 PM. Click to view previous post history.

  2. #12
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    Andreas, the articles were written by research chemists from paper manufacturers. Extracts were précised and also published in trade & more serious photographic magazines, and I'd guess the popular photo mags as well. The specific VC brown safelights were produced because some of the "Red" safelights weren't safe enough under certain circumstances, for instance smaller darkrooms. For all practical purposes you wouldn't spot the problem unless you are specifically trying to get maximum contrast from a VC paper at Gd 4.5/5.

    VC papers aren't pure orthochromatic products, but your assertions about a Red safelight were exactly what was assumed to be correct, then it was found to be otherwise. It's 22 years or more since the articles were published, I can't remember where I first read them, it may well have been the Journal of Photographic Science.

    What I assure you is I had problems myself after moving darkrooms with a new Red safelight filter, and after changing to the manufacturers Brown VC filter the problem was solved - a full contrast range with Ilford VC papers. I can also remember discussing this issue over a meal with a senior research chemist, and the sales guys for Film/Paper (Emulsions) and Chemistry, at Ilford at the time, and they were fully aware of it.

    Lastly ask yourself why would any manufacturer need to manufacture a specific VC Brown safelight filter, if there were no problems with existing Red safelights.

    Ian

  3. #13
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    It's worth adding:

    Most photographers planning to make high (or low) contrast images start at the negative stage. How many photographers actually use Gd 4.5/5 or Gd 00/0 with VC papers. In 30+ years the only time I've needed to has been when printing other peoples negatives (clients).

    I first came across the safelight problem when printing examples of contrast grades from the same negative, Gd 4 was the highest achievable with a Red safelight filter, changing to the VC Brown then GDs 4.5 & 5 were there too.

    Ian

  4. #14
    ath
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    Thanks for the very interesting response, Ian.

    As for the selling of brown filters - there are also other reasons for them, see Johns initial question. I wouldn't judge their existence as a "proof".
    Regards,
    Andreas

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    With regard to this "red filter problem", which specific papers "still in production" should we concern with? Thank you.

  6. #16
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    You're ever the sceptic, Andreas, you should read the posts today by Martin Reed about Kentmere/Centennial Printing Out Paper and then remember how you insisted in posting that the equipment was already ripped out and scrapped.

    Ian

  7. #17
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    Quote Originally Posted by DannL View Post
    With regard to this "red filter problem", which specific papers "still in production" should we concern with? Thank you.
    All VC papers, but only if you can't achieve a full range of contrasts.

    Ian

  8. #18

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    Quote Originally Posted by Ian Grant View Post
    All VC papers, but only if you can't achieve a full range of contrasts.

    Ian
    If you can't achieve a full range of contrasts, the probems can be solved by using a different safelight?

  9. #19
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    Quote Originally Posted by DannL View Post
    If you can't achieve a full range of contrasts, the probems can be solved by using a different safelight?
    You got it in one, or move your safelight as far away from the paper as possible
    Another option is wire your safelight filter to a dimmer switch and just turn it down.

    Ian

  10. #20
    CBG
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    Quote Originally Posted by ath View Post
    Never heard this before. I'd like to hear the reasoning behind this.
    The conventional explanation. VC paper has two emulsion layers, one sensitive to green light, and one sensitive to blue light. Thus the perfect environment for VC paper has no ambient blue or green light. If your safelight "leaks" any blue or green at all, that is to say if your safelight filter is not perfect, you'll get some fogging eventually. Safelight filters gradually degrade as they get exposed to the light and heat from the bulb, and begin to get leaky as time passes.

    Despite all that, generally one assumes the filter was perfect - no blue transmission and no green transmission, on the day it was manufactured. I'd guess the filters are actually at best only very near perfect, thus the time and distance limitations on exposure to the safelight.

    Best,

    C

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