My friend and I were discussing disposable cameras, and more specifically how they work internally. I told him “either way, don’t try to open one up unless you really don’t care about the film- or if you’re in a dark room.” He asked how he could see in a dark room, and I smugly told him if you use red cellophane on an incandescant, filtering out all but the red light, the film wouldn’t be affected.
He wanted to know why red light wouldn’t ruin the film… I wondered about that, and responded it has to do with the longer wavelength not affecting the film as much (was that bullshit?) - to which he asked, “then why can we take pictures of red things, and have the colors look right?” and I had no answer. Any ideas?
Erm - red light WILL ruin your film, unless you’ve somehow managed to get ahold of a roll of orthochromatic black-and-white film, which ain’t exactly common these days. These days virtually all film, including black-and-white is panchromatic, which means it is sensitive to all colors of visible light (and thus would be exposed if you shined any color of light on it, including red).
You’re probably thinking of Hollywood movies and TV shows where some is depicted fumbling around in a darkroom under reddish-orange light while developing film or making prints. This is only partially accurate. Black and white photo paper is indeed not very sensitive to red light, and so it can be handled under these lights (called “safelights”) for a time without the risk of ruining it, and the same goes for orthochromatic film. Not that you’d really want to shine a 300-watt amber spotlight on this stuff or anything - you’ll notice that the safelights are usually dim, and for good reason.
Red lights can only be used in darkrooms when you’re working with monochrome film and paper; the film is not very sensitive to red light (this is evidenced by the fact that red objects in a BW photo often come out very dark on the print).
The real red lights in darkrooms (as opposed to the ones you see on Columbo) are very dim.
There is (IIRC) a similar light for use with colour photography, but as it needs to avoid emitting wavelengths to which the colour film is sensitive, this doesn’t leave much to play with - the light is a very dim murky greenish colur I think - many people who process colour (manually in a darkroom as opposed to one of those photo processing monster machines) work in total darkness by touch.
Right. I have worked in dark rooms and when developing film or printing color I am always in the dark. And we mean really dark. Not dark as in you need to turn on a lamp to read but NO light at all! When printing B+W prints you can use a dim safe light. One darkroom I worked in had a TV with a red gel over it so we could watch TV all day.
When processing black and white film, total darkness is required and must be done by feel. (It’s pretty easy once you’ve had a little practice.) However, black and white photo paper can be used under very dim, red safelight. Just enough light to be able to see what’s going on. Color photo paper is too sensitive and usually requires total darkness. I’ve never personally done any color processing, though.
I have a color darkroom setup and you can, in some circumstances, use a very dim green lamp. These safelights all have filters with properties tailored to the specific film or printing paper type, I must have about 6 different filters for my safelights. But safelights aren’t perfectly safe, if get them too close to your film, they will fog the film anyway.
BTW, you can also inspect panchromatic B&W film under a dim green safelight, at the halfway point in development. Lots of the old-school photogs, especially people using cut sheet film, used to inspect the film at the halfway point and decide how much longer to develop.