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Thread: About red safelights. How much red is damaging for the paper

  1. #1

    Lightbulb About red safelights. How much red is damaging for the paper

    Hi.

    I have a darkroom and I need to shoot a high quality video of the printing process and the safe lights are not strong enough for my purposes. I was wondering how convenient is it to put a large red filter over a medium window (at the moment is covered with black plywood) so I can work with daylight and still prevent the paper from fogging. ¿Somebody recommend doing that? ¿How red (dense) should the filter be? ¿How can I measure that? ¿What's the less sensitive paper to red light that I can use to prevent fogging? I guess is a matter of trial and error but I need some opinions first.



    Thanks a lot



    Camilo

  2. #2
    John Olsen
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    Re: About red safelights. How much red is damaging for the paper

    Well, they're called safe lights for a reason. I tried using a red LED in my safelight and it was mighty convenient, but fogged the paper after a few minutes. I had to dim it to the point that it wasn't much brighter than my regular safelight before I was "safe" with it. Red Roscoe filters over a window will be way too much, not that I've tried it myself.

    You could gain some leeway by processing your prints face down in the trays, unless the point of the video is to show the image emerging.

    Or you could fake it by showing a series of short sequences with a different paper in each, so that the paper in the developer was not the same one exposed under the well-lit enlarger.

    Sounds like a real challenge! Let us know how you do it.

  3. #3

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    Re: About red safelights. How much red is damaging for the paper

    The minimal experience I have had with a friend doing some videography in my darkroom, is that you will not get brilliant imagery, but quite reasonable imagery with Ilford 902 filters.

    These are a light brown filter, the ones we used were 203x254mm filters at 1.2m from the paper with a 15W tungsten light globe as the light source. Tripod mounting the camera was another must I seem to remember. Smaller safelight filter sizes, even though they had the same light power source, were a bit harder for the camera to use.

    Around 30 years ago at a photographic exhibition, Ilford Australia had a working darkroom on their stand. The darkroom had large plexiglass type windows covered in a rubylith type of material which allowed them to expose and develop paper while people stood outside and watched. I'm not saying it was brilliant, but for the purpose, which was to show darkroom developing, it was great.

    You'll probably need to fudge it a bit though, think like a wildlife film maker, the animal being predated upon is one animal, while the animal shown grazing/feeding is often different but in the film shown to be the same animal.

  4. #4

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    Re: About red safelights. How much red is damaging for the paper

    Quote Originally Posted by CamiloRozo View Post
    I was wondering how convenient is it to put a large red filter over a medium window (at the moment is covered with black plywood) so I can work with daylight and still prevent the paper from fogging.
    That will most likely be challenging, as daylight is pretty powerful and is of course full spectrum, so any filter you use will have to be *extremely* effective. In practice, filters can be good, but they're never perfect; they will attenuate some wavelengths almost completely - but almost is not necessarily good enough.

    Still, I'm not worried, because there are obvious solutions.

    1: For your video, you could work with lights that are not necessarily entirely safe; yes, the prints will be compromised and may be somewhat fogged, but for demonstration purposes this can still be OK. Just make two sets of prints, one for the darkroom scenes where the prints in the end don't come out perfect, and prints that are made under the appropriate conditions and turn out OK to show the end result. The beauty of film is that we can play a few tricks on reality to convey the message, right?

    2: It's actually possible to have quite high light levels with B&W papers - as long as the light is appropriate. Not just any red led light will do as John Olsen experienced. I'd start by trying to find 660nm LED floodlights; they're used for plant growth a lot these days. The benefit of these is that they tend to have less secondary emission in the green part of the spectrum than the more common 620nm leds. This is likely also the cause of John's mishap with led lighting - it's not so much the amount of red light, but the problem of non-red light components that leds emit. They're not perfectly narrow-band emitters in practice! A second part of the solution can be to apply additional filtering to the leds. Rubylith is getting hard to come by these days, but is *very* effective in filtering out shorter wavelengths. You can take red leds and apply one or two layers of rubylith to get pretty 'clean' red light that will be safe for many minutes for regular B&W paper. This is what I have in my current darkroom - plenty of light, and modern equipment would have no problem recording video under these conditions at all (but all I have is a fairly dated EOS 7D mkI ...luckily I don't do much with video). A final part of your solution may be to use warmtone paper. This is generally a few stops slower than neutral/cold tone paper - this also means it fogs less easily. Hence, you can get away with using lights that are not 100% 'safe' for neutral B&W paper and still get prints free of fog.

    If you combine the above, I have no doubt at all that you can successfully make decent quality video from darkroom sessions AND get prints from those session that are perfectly OK in terms of fogging etc.

  5. #5

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    Re: About red safelights. How much red is damaging for the paper

    I use 12 volt LED strips with a 9 volt suppy, 5 meter.
    I might have another wavelength than most? Even 12 extra break light work well.

    Sent fra min SM-G975F via Tapatalk

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    Re: About red safelights. How much red is damaging for the paper

    Quote Originally Posted by Oslolens View Post
    I use 12 volt LED strips with a 9 volt suppy, 5 meter.
    Any particular theory behind this? Given the fact that most led strips are simply a couple of leds in series with a current limiting resistor, this approach would either have the leds burn dimmer than they're supposed to or not light up at all (particularly white and blue strips). It's unknown to me if reducing the forward current would eliminate the green secondary emission peak. It will shift the emission peak of the leds very slightly, but this won't be enough to make a real-world difference in this application.

  7. #7
    jp's Avatar
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    Re: About red safelights. How much red is damaging for the paper

    https://www.youtube.com/watch?v=U9cghjFyzlM

    I did this in my darkroom with my Nikon d600 for a video cam and used a tracklight with red LEDs from superbrightleds.com. I expect newer cameras would do even better.

  8. #8

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    Re: About red safelights. How much red is damaging for the paper

    Quote Originally Posted by koraks View Post
    Any particular theory behind this? Given the fact that most led strips are simply a couple of leds in series with a current limiting resistor, this approach would either have the leds burn dimmer than they're supposed to or not light up at all (particularly white and blue strips). It's unknown to me if reducing the forward current would eliminate the green secondary emission peak. It will shift the emission peak of the leds very slightly, but this won't be enough to make a real-world difference in this application.
    Only reason is to have them last longer, never burn out vs 10 or 50 thousand hours. 12 volt seems to heat them a tiny bit too much in my taste. I could have used 10 or 11 volt, but that would be another, bigger power supply.

    Sent fra min SM-G975F via Tapatalk

  9. #9
    ic-racer's Avatar
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    Re: About red safelights. How much red is damaging for the paper

    I know video editing is tedious but if you are shooting digital, then faking it should be no problem. Even grade school children could make an image appear on white paper with a pre-written 'dissolve' function. When I was doing digital in the early 1980s, I had to write my own routines for image manipulation. Now days it is so easy.

  10. #10
    Pieter's Avatar
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    Re: About red safelights. How much red is damaging for the paper

    You could perform the Kodak safelight test. K4_Safelight_1106.pdf

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