Red lights in darkroom

<p>What's the deal behind red lights in darkroom ? I have came across several posts that stated it is ok to use red light when loading, developing B+W films, but not for color films, but on wikiHOW it states never use Red lights when loading B/W films. Who is correct ?</p>

<p>You can use red or yellow lights in a darkroom where you are doing printing. Photo paper is not sensitive to these colors. In the "old days" black and white films were not sensitive to red light. Modern litho films are also red insensitive.</p>

<p>Modern consumer B&W films, however, are panchromatic and sensitive to the whole spectrum of light. Having said this, according to various technical publications a very dim green filtered light can be used sparingly to inspect the development process of panchromatic films. I suspect the faster the film the less safe this technique is.</p>

<p>Robert's right , but a very dim green filtered bulb can be used when loading film. Better to do it in the dark. </p>

Red safelights were made for orthochromatic film. Not safe for panchromatic or color film. I still see adds on the net for orthochromatic film but I don't think it's very common now.

<p>Panchromatic film (more-or-less sensitive to all colors) has only been around since 1906. During the 1930s, lots of people shot on orthochromatic (not red sensitive) because it was cheaper. However, since World War II (1939-1945) it has even become hard to get orthochromatic film. So it's not surprising that some of the books (which are often mindlessly cribbed from still earlier books) haven't quite got the message yet. :P<</p>

<p>Even the green lights are not really "safe" for panchromatic films like all the usual ones (Tri-X, etc.) on the market today, as noted. Total darkness is better. Unlike the old othochromatic films which could be developed by inspection (like paper prints) under red light, trying that with green safe lights will fog pan film.</p>

<p>I do remember, fondly, developing 620 ortho film by inspection under safelights in the kitchen when I was a kid. Timer- we don' need no steenkn timer!</p>

<p >All films, be they color or black & white receive their light sensitivity from three salts of silver. In order of ISO, they are silver bromide, silver chloride, silver iodine. These salts resemble table salt in appearance except silver salts are minuscule crystals, and all three are slightly yellowish in color. Because they are yellow they absorb blue light. Furthermore films and papers are only sensitive to blue unless specifically treated. These films and papers we call “blind” because of their lack of sensitivity to red or green light rays. Being insensitive to red or green means the darkroom can be illuminated with a safe-light, either red or green, also yellow. Yellow is common.</p>

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<p >In 1873 H. Vogel discovered that silver crystals could be caused to be sensitive to green light by use of sensitizing dye. Vogel dyed unexposed crystals red-blue, this extended their sensitivity into the green region. The dyed crystals never lost their sensitivity to blue thus films were now sensitive to blue and green and called othrochromatic. Now only a red safelight could be used.</p>

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<p >The next breakthrough occurred in 1904. E. Honig and B. Homolka succeeded in dying the crystals to achieve both red and green sensitivity. As before, the crystals never lost their sensitivity to blue. Now for the first time, films could be made sensitive to the three primary colors of red, green, and blue. The film is called panchromatic. The use of a red safe light was prohibited however since films are least sensitive to green, a feeble green safe light is permissible. However, it is too dim to be of real value, the green safe light is mainly used to prevent one from tripping in the darkroom. Some can use the feeble green to develop by inspection. I was never successful using the green safe light. </p>

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<p >Most photo papers remain only sensitive to blue thus the use of a yellow safelight (blue blocker) is common practice. Multiple contrast papers are sensitive to green and blue thus special safelights are required. Usually these are equipped with sodium lamps as they emit a narrow spectrum of light.</p>

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<p >All safe lights must be tested for legitimacy. </p>

<p>And why a weak green?<br>

Under low light intensity the cones in our eyes are asleep while the rods respond. I believe this is called scotopic vision.<br>

The peak response in scotopic vision (low light) is around ~ 510nm, near the bottom end of "green". So, for a given watt density our eyes in a 'darkroom' are much more sensitive to green than to red or blue. Thus, only a wee bit of green goes a long way for us bipeds but impacts panchromatic film less.<br>

At least the internet seems to imply that.<br>

Jim</p>

I tried to try to use a green safelight when I was a kid but could not see enough to make it useful at all so went with total darkneess and a timer.