I have some minor light leaks under the door of my darkroom that in almost 20 years of use have never lead to fogging. It takes me a minute or two of complete darkness to see them. However, when loading film onto reels, I don't want to take any chances and either make certain that the "minor" leak is sealed or that it is dark outside of the darkroom.
The double doors into my darkroom have 1" gaps at the floor, thus letting in enough light that you can see the floor quite well once your eyes adjust. I have seen no evidence of fogging from this, and in fact the darkroom itself has been in use for 30+ years. The double doors have a kind of collimating effect, there is almost no light coming up off the floor, though it can make your shoes glow.
For tray dev of IR and fast films, I put a lid on my trays.
Bear in mind that the dark-adjusted eyes have rather spectacular sensitivity. You can have unmeterably low levels of light, maybe 10-20 stops below what you can meter, and still see around quite well. IIRC the dark-adjusted eye can see the light from single candle at one mile distance.... quite near single-photon sensitivity.
Thanks for the very interesting information about the sensitivity of the eyes. I went back into my darkroom....at first everything was black...then one could note the smallest bit of light coming from around the light seals surrounding the door and from the saddle of the door on the bottom....so, the light adjusted eye will see such faint traces of light after the eye accommodates to the conditions. However, I have never had problems with fogging of film or paper, even with TMAX 400.....however, I'm going to be even a bit more careful to load my holders on the shelf as far from the door as I can with my body between the holders and the door....as unlikely as such would be, I don't want to start having any problems now.
A single candle at one mile........rather amazing....even a retired MD can learn facts that were not previously known...:}
I, too can see light leaks around my door after I've been in there for a while. I also have glow-in-the-dark stars stuck on the walls and the enlarger head to help me maintain my orientation and not hit my head. My gralab also has glow-in-the-dark letters.
The way I see it, we are dealing with, at the most sensitive, camera film here. To get a grasp on how much light is traveling into my film-loading area, I once set a sheet of white paper there. Even after my eyes are well adjusted, I can't see it. Even if I could, suppose I wanted to take a picture of that sheet of paper by exposing the film in a camera, behind a lens, how long would I have to leave the shutter open? I would guess many hours, possibly infinity, for anything to register on the film, and that would be behind a lens aimed at a white sheet of paper. So I don't worry about having my film out in that same level of light for the few minutes it takes to load it. Even in moonlight, my camera exposure times would be many minutes, and at that level of light, I can easily see someone standing next to me, see my hand in front of my face and walk around without worry.
Ventilation is important since you want a source of fresh air to breathe. You would want the out going air to be on the other side of the chemical trays from the incoming source and you being on the incoming side. If you can't construct light traps, a simple and inexpensive light "seal" can be made by getting black opaque plastic sheeting at a garden shop or Home Depot. Fold it in a couple of thicknesses and attach it to a dowel stick on top and one on bottom. Place a couple of "L" hooks above the door. You just hook the dowel above the door and extend it enough to make a light trap and the bottom dowel holds it down. It has worked for me for over thirty years. You can also block out windows as well. (If the sides need to be secured, use Velcro that comes with adhesive.) The whole setup can be removed when not in use.
When I develop sheet film in a tray, it is exposed to the darkroom light for about 30 minutes. I need a light proof environment in the darkroom. Moonlight or light leaks under the door are not acceptable and highly unnecessary.
The single-photon assertion is a bit controversial as it depends critically on the angle at which the light is seen (b/c of the distribution of rods on the retina) and on the condition of the eye and how many carrots the subject has in his/her diet ;) Turns out that the brain filters out much of the noise containing the single-photon information. But, in the statistical sense, the scotopic vision is actually sensitive to a single photon.Quote:
On a clear dark night the eye can see a lit candle from 30 miles away
Regarding light under the doors, of course the very safest policy is to strive for complete darkness, but I am reporting, with very high confidence, that a bit of light under the door in my darkroom has had no measurable effect. And I have worked with IR film extensively.
There are many things in photography that people sweat and fuss over but which ultimately turn out to be moot most of the time. This is not the right profession for worry-warts: their creativity can simply grind to a miserable halt. There are just too many potential technical pitfalls to obsess over: MLU, 1/FL, aperture for best MTF, center post or not, base fog... etc. etc. Best policy is to experiment, establish your own best practices, and go with what works for you.