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#1
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Darkroom safe light
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. |
#2
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Darkroom safe light
On Feb 2, 10:42*am, piterengel wrote:
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. 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. |
#3
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Darkroom safe light
"piterengel" wrote
[a] red safelight works [better] ... Is this correct? 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, Cleveland, Ohio Darkroom Automation: F-Stop Timers, Enlarging Meters http://www.darkroomautomation.com/index.htm n o lindan at ix dot netcom dot com |
#4
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Darkroom safe light
"piterengel" wrote in message ... 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. 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 Los Angeles, CA, USA |
#5
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Darkroom safe light
"gr" wrote in message
... In general photo papers are sensitive to green and blue. Yellow can be safe, red is safer. Brown is "who knows". Brown really is Who Knows! It's a strange color. It cannot be 'seen' except in contrast with another color of greater luminosity. |
#6
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Darkroom safe light
jjs wrote in message ... "gr" wrote in message ... In general photo papers are sensitive to green and blue. Yellow can be safe, red is safer. Brown is "who knows". Brown really is Who Knows! It's a strange color. It cannot be 'seen' except in contrast with another color of greater luminosity. 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 Los Angeles, CA, USA |
#7
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Darkroom safe light
jjs wrote:
"gr" wrote in message ... In general photo papers are sensitive to green and blue. Yellow can be safe, red is safer. Brown is "who knows". Brown really is Who Knows! It's a strange color. It cannot be 'seen' except in contrast with another color of greater luminosity. 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. |
#8
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Darkroom safe light
On Feb 2, 1:42*am, piterengel wrote:
Or, better, red light is "more universal" than light brown one. Is this correct? 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 |
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