Testing Your Darkroom's Darkness

[Leonard Metcalf]

I've sat in the complete dark in my room for over 10 minutes. I can't see anything. I think I'm just going to load my film in a dark bag, and then try the tray developing. That should eliminate one variable. If the film looks good after that, I'll try loading my carriers in the room.

Well... that is the test I have been using for years... ten minutes and you can't see any light leaks, when you look around, and you have a room good enough for me..

[photobymike]

Something that a lot of photographers overlook is the florescent lights. Long ago i was having a problem with fogged film in my darkroom. I sat in the dark for 30 or 40 minutes waiting for eyes to adjust.... Zazam my lights were glowing and occasionally flashed .. it was dim but it was happening. I had to remove the florescent lights and go with incandescent lighting. all was fixed.....

[Arne Croell]

Something that a lot of photographers overlook is the florescent lights. Long ago i was having a problem with fogged film in my darkroom. I sat in the dark for 30 or 40 minutes waiting for eyes to adjust.... Zazam my lights were glowing and occasionally flashed .. it was dim but it was happening. I had to remove the florescent lights and go with incandescent lighting. all was fixed.....

True, fluorescents can be a problem that way. It depends a lot on the phosphor being used. In my experience, cool white tubes tend to be more of a problem with phosphorescence than warm white ones, but it might also depend on the manufacturer. In any case, spending 15-30 minutes in the dark to let the eyes adapt should show any light leaks. Fully dark-adapted eyes (about 30min) are quite sensitive to light.

[Doremus Scudder]

Your eyes are very sensitive AFTER they have become dark adjusted (as Lenser observes in his post above). It takes about 30 minutes to reach full adjustment, but most of it happens in the first 5-10 minutes. After your eyes are dark adjusted, they are sensitive enough to detect just a few photons at a time. http://en.wikipedia.org/wiki/Night_vision

So, test your darkness with dark adjusted eyes. First look around for light leaks; under doors, around windows, cracks in the wall, seams between beams, etc. Crawl around, stand on chairs, change your head height and points of view. Do a few 360° turns from different positions. Identify and block whatever leaks you find.

Next, try to put your point of view where the light sensitive material is going to be, e.g., in the tray positions, loading table, etc. and look for more leaks. If this is impractical (i.e., requires too much limbo dancing) place a sheet of white paper in those critical positions and check for reflections.

If you see nothing, it's safe for film and paper.

Do a safelight test for your paper; it's easy and will give you peace of mind. I like knowing that my fairly bright darkroom is safe for more than 20 minutes for my enlarging papers.

Oh yeah, ditch the flourescents or make doubly sure they don't glow after a few minutes. Also, mark light switches, etc. so you don't accidentally switch on the white light when you don't want it. I've ruined more things that way than with light leaks...

That's all there is to it.

Best,

Doremus

[BetterSense]

I can actually see light leaks in my darkroom, but it's never been a problem. I also have 2 gralab timers and some glow-in-the-dark sticky stars in there, so I can often see my hands or what I'm doing *by silhouette* only. After being in there for a very long time, such as when rolling 35mm bulk film, I can start to see white things by reflection, barely. I'm not fixing it though, because it hasn't been a problem. If you think about it, if I wanted to take a picture in there at f/2, how long would I have to have the shutter locked open? I'm not sure if even several hours would result in density on the film, and film with no lens approximates f/1.

[ic-racer]

Hey folks,

Do you any of do any actual testing of your darkroom's darkness? Like leaving film or paper out for a long period of time or some other test.

Just curious.

The test for light leaks occurs at the same time as you do the safelight test.

In terms of testing for total darkness and ability to manipulate unexposed film, you can just use your eyes for that one. Your eyes are more sensitive than the film.

[BetterSense]

I totally agree that your eyes are more sensitive than the film...unless it's IR film, or unless there is UV in your darkroom from fluorescent light, or unless your film is orthochromatic and the light source is red. But other than that.

Also, there is a Kodak tech publication about safelight testing. I highly suggest following their procedure, because it is much better than the simple 'leave a piece of film/paper sitting out' test, and it's not any harder to do.

[Steve Smith]

Mine's not completely lightproof but it's dark enough for making prints. I think I would have to improve it a bit for handling film in though. At the moment I use a changing bag.


Steve.

[jon.oman]

I built a new darkroom this last fall / spring. There is only one opening to the outside of the darkroom, the door. My darkroom is an 8 by 16 foot room at the back of my 16 by 24 foot shed. The shed has a roof vent on the ridge, and two flat vents at each end. When I close the shed door, and arrange the 'commando' cloth curtain in front of the darkroom door, it provides enough light proofing. I used drywall for all internal walls and the ceiling. I can sit in the darkroom on a bright South Carolina day for an hour, and not see a single light leak. I think I'm safe....

[Kevin Crisp]

If you sit in the darkroom for 10 minutes with the lights out and your eyes open and you can't see any light leaking in you are fine.