VC Safelight

Discussion in 'B&W: Film, Paper, Chemistry' started by Anscojohn, Feb 14, 2008.

  1. Anscojohn

    Anscojohn Subscriber

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    Hello All,
    Back in the Pleistocene Era I worked as a printer in a BW lab, using Dupont Varilour paper. Our safelights were the Dupont kind of off brown and were really great because it made it very easy to judge a print under safelight. I know red safelights are safe for VC but I find it much harder to judge a print under red light. I have two unused safelights with 5x7 OA filters. Any suggestions about making a cheapo conversion? TIA

    John, Mount Vernon, Virginia USA
     
  2. Erik L

    Erik L Subscriber

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    Hi John, you can buy 5x7 filters from bh photo for around 10 bucks I think
    regards
    Erik
     
  3. Anscojohn

    Anscojohn Subscriber

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    Thanks, Erik,
    I'll check them out.

    John
     
  4. dancqu

    dancqu Member

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    OA. Is that not a yellow-ish green? How about
    an orange or red 15 watt? Dan
     
  5. ath

    ath Member

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    There are some VC papers today which will have issues with other than red safelight.
     
  6. Ian Grant

    Ian Grant Subscriber

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    Use the closest you can to the manufacturers recommended safelight filter. That may not be a Red filter. There can be a problem with red safelights with VC papers which causes a reduction in the achievable contrast range, it's similar to using pre or post flashing to reduce contrast.

    This was the reason some manufacturers like Paterson began making special VC safelights/filters.

    Ian
     
  7. ath

    ath Member

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    Never heard this before. I'd like to hear the reasoning behind this.
    It's clear that even red light is not entirely safe, but (provided same intensity) it cannot be more harmful than light with shorter wave length.
     
  8. Ian Grant

    Ian Grant Subscriber

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    Andreas, go and look at some of the Agfa data sheets for their multi-contrast papers, they have a long section on safelight fogging.

    This was from an Agfa datasheet, but it also applies to the problems found with some red safelights and VC papers. There have been a number of magazine articles written about the issue but most pre-date the internet.

    Ian
     
  9. ath

    ath Member

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    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.
     
  10. Anscojohn

    Anscojohn Subscriber

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    Man, this is getting complicated.

    John, Mount Vernon, Virginia USA
     
  11. DannL

    DannL Member

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    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 a moderator: Feb 15, 2008
  12. Ian Grant

    Ian Grant Subscriber

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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
     
  13. Ian Grant

    Ian Grant Subscriber

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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
     
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  15. ath

    ath Member

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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".
     
  16. DannL

    DannL Member

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

    Ian Grant Subscriber

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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
     
  18. Ian Grant

    Ian Grant Subscriber

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    All VC papers, but only if you can't achieve a full range of contrasts.

    Ian
     
  19. DannL

    DannL Member

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

    Ian Grant Subscriber

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    You got it in one, or move your safelight as far away from the paper as possible :D
    Another option is wire your safelight filter to a dimmer switch and just turn it down.

    Ian
     
  21. CBG

    CBG Member

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    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
     
  22. dancqu

    dancqu Member

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    Simplify your life. Switch to Graded. A yellow to
    orange-ish safelighting will flood your darkroom.
    Easy to see about and evaluate your prints
    as they develop. Graded papers are blue
    sensitive only. Dan
     
  23. Anscojohn

    Anscojohn Subscriber

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    Dan
    Yeh, but I want it ALL. My first choice is graded: in fact I have some original French made Zone VI Brilliant still in the freezer; ditto for the old Oriental Seagull. But I sometimes use VC paper and would like to get rid of those red safelights. I bought an amber LED bulb but it fogs the VC. Plus, of course, frugal me would like to do it all as cheaply as I can.

    John, Mount Vernon, Virginia USA
     
  24. Bob F.

    Bob F. Member

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    Brown is a mixture of red and green light and VC paper is sensitive to green light. Looking at Ilford's safelight filter responses we see that the light-brown filter (902) is a high-pass filter that allows everything above approximately 560nm through: from a deep green through red and into the IR. Likewise, the dark-brown (904) filter allows everything above 575nm.

    So, in practice, a "brown" filter allows as much red light through as a purely red filter does... In addition, 560nm is just within the published sensitivity range of MGIV. This implies that in fact lower light levels may be required than with a pure red (>620nm(ish)) light.

    I suspect the advantage of the "brown" filter is that being less monochromatic it allows greater clarity at lower light levels. The human eye is relatively insensitive to red and most sensitive to green, so people will tend to have brighter red lights than with lights emitting at lower wavelengths in order to see with a given level of clarity.


    I use amber (590nm) or orange (615nm) LEDs in a bright darkroom for VC paper. These have the minor irritation of being highly monochromatic and I keep meaning to mix 3 different colours in one safelight (red + orange + amber) to make a (theoretically) more comfortable light...

    Re' the observation that an amber LED lamp fogged: commercial LED lamps intended for home use seem to often emit all over the place - presumably due to cheap LEDs and hopeless driver circuits. With amber being so close to the sensitivity of VC paper, you need quality LEDs driven with low-ripple d.c at their rated current to avoid out of band emissions. Also, a similar "amber" lamp I bought turned out in fact to be green which may be another possible cause of the problem...

    Nevertheless you may simply have it too bright. Shade it, or otherwise reduce the light, and do the usual pre-fogged paper safelight test. If you are not familiar with the test, download the Safelights fact sheet from the Fact Sheets menu at http://www.ilfordphoto.com/products/product.asp?n=48&t=Photo+Accessories+&+Equipment for how to test effectively (Kodak has a similar one on its site too but I don't have a link to it). If it still proves unusable, try again with an orange LED lamp which, emitting further away from the sensitivity of the paper, may work.

    My bottom-line is: choose brown or orange if like me you dislike red, but whatever you choose, do test it.

    Have fun, Bob.
     
  25. ath

    ath Member

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    Ian, it's hopeless with you. Learn to read properly before accusing others.
     
  26. john_s

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    If you're relying on LEDs being monochromatic, you might be surprised to view their light reflected from the base of a CD at the angle that gives the "rainbow" effect. I think it's hard to estimate how much green is in the light this way, but it often reveals the presence of it.

    With an incandescent lamp wired with a dimmer, an advantage of dimming is that it shifts the colour of the light towards red. With LEDs, I have read that lowering the current they are passing does not alter the basic colour, but it narrows the spectrum, and this might be helpful too. I can't verify this, I read it somewhere.