How to know if it is truly dark in a darkroom?

rbiemer

rbiemer

Unabashed Amateur
Local time
12:55 PM
Joined
Sep 17, 2004
Messages
5,092
I am gearing up to start shooting a 4x5 camera and have most of what I need.
I will need to load sheet film holders and to load the daylight tank for developing and I have a closet in my bathroom that might work well for that. It is inside the bathroom which has no windows and it has some conveniently sized shelves so I can layout my film and film holders and the light switch for this closet is inside the closet so no one (except me) can accidentally turn the light on while I'm in there.

I am not sure, however, if this closet is truly dark. So, how do I test it?

I could just buy a changing bag but I'd rather spend that money on film.

Is it a simple as going inside the closet and waiting 10 or 15 minutes and if I still can't see my hand, it's dark enough?

Thanks!

Rob
 
The human eye is remarkably sensitive. More so than any camera or electronic meter that you can afford and that does not need liquid nitrogen cooling. If you cannot see any light leaks after five to ten minutes in complete darkness, it generally is dark enough.

In doubt, put a half obscured sheet of the fastest film that you use onto your table for a couple of minutes, process and compare the halves - there should be no difference.
 
Look for light leaks as said above. I have just used my long planned darkroom for the first time and all has gone well but the initial testing showed unusual and unexpected light leaks which needed rectification. Look around all doors and joins. I had light coming around an internal wall and wriggling past a light seal. Once all seems good enough you can be double sure by using your darkroom at night with the house lights off.
 
I think it takes about 30 minutes for the eyes to reach full dark sensitivity. I've always spent close to that length of time to test a film loading room. Have a piece of paper or index card to place in different areas to see if the leaks actually travel. Usually the bottom of the door will need something- a towel or blanket if you don't want to weatherstrip it. If there are very minor leaks visible but I will be blocking them with my body I don't worry. But the typical glow around door jams I will seal- thin foam usually works well; a blanket hung across the door opening has been a temporary solution at times.
 
Wait 10 minutes. Move your hand in front of your face. If you can't see any movement, it's dark enough.

Obviously there's scope for personal variation but this has worked for me since I read about it decades ago.

Cheers,

R.
 
Regular bathroom door is going to leak the light from outside. Gap is on the floor and sides will leak the light. Bathroom light fixture might radiate light after it is turned off, for few minutes. And modern power outlet in the bathroom might have green light.

Usually I'm waiting for sun totally down. Closing windows and doors at the room where bathroom is, turning light only in the room beside bathroom and blocking the light on the power outlet.
 
Try using peripheral vision, the light sensitivity is greater then straight ahead

You need to keep eyes steady and pay attention to the sides, not move. Eyes to the side

The best test I've done though, is a sheet of phot paper partionally covered, let it sit for a couple mins and develop it, if you see a difference btw covered and uncovered - there's a problem
 
As above, simply waiting and looking. I have some tiny light leaks when the sun is shining brightly, but as Dan as said, they are behind me when I am loading film reels and I certainly block them with my girth. They are not likely capable of fogging film, but as an extra precaution I wait for a non sunny day, evening, or cover the offending window across the adjoining room if I have to load film holders or break down a 400 foot roll of bulk film. I will eventually get around to caulking the gaps that cause the leak, but they are extremely hard to reach with a caulk gun or a staple gun, tape doesn't stick to the roughsawn lumber of my ceiling beams, and I'm a bit too lazy.

Pushpins holding a blanket up over the door is extremely effective, if this will be a more dedicated space I like using the felt style weatherstripping that installs with staples around the door. It is easy to replace if it gets worn and there is no gummy goo from an adhesive to deal with.
 
Since film exposure is determined by duration and quantity of light, small light leaks are unlikely to affect normal film processing procedures if you're putting it into a daylight developing tank. Extended time in open trays might be more risky. I've had some pretty leaky home darkrooms in the past but I can't recall any negative (ahem, sorry) effects when loading film into closed tanks.
 
Of course, the easiest approach is to use a windowless cellar with impeller and extractor fans and a door opening into a (dark) interior room, with the door further light-proofed with on the opening side. But this is something of a counsel of perfection...

Cheers,

R.
 
sevo said:
The human eye is remarkably sensitive. More so than any camera or electronic meter that you can afford and that does not need liquid nitrogen cooling. If you cannot see any light leaks after five to ten minutes in complete darkness, it generally is dark enough.
Click to expand...

Exactly that.
I've had several darkroom in my photography life at different places, and I've always used that method, which works perfectly.
Working in a darkroom is just wonderful, and even after decades I still enjoy it today the same way as in the beginning :) .
 
You still may 'see', but in your minds eye, with your fingertips. I find that in a completely dark space I see the reel I'm loading. It's a weird sensation and at first I thought the space was not totally light proof, but even ISO 400 film showed no trace of being fogged when left out for at least 15min.
 
Be safe. If you see anything after 20 minutes, fix it.

covering half the sheet of film is as invalid as the safe light test with coins.
 
See where any light leakage is by checking with lights outside the door on, and if natural light could come in, do this check in the middle of a sunny day. Seal windows with real black out plastic (Ultrafine/Photo Warehouse sells it) and black gaffer tape, door frames with weather stripping, and door bottoms with black out plastic taped to the inside of the door down to the floor, plus a little more, with a rolled-up towel "sealing" the plastic to the floor and door frame.

Then use the darkroom only at night with all lights outside the darkroom out and nearby room doors closed.
 
One likely place for a light leak is the space between the closet door and the floor. Putting something. permananetn or temporary, to block that light is a good idea. Light around the other three edges may or may not be effectively stopped by the stop moldings. If the door does not close tightly, a means can be added to hold it shut. I use a hook and eye latch to pull the door in tight and hold it. Also keeps anyone from opening the door while you are loading. I also use a thin gasket material to held seal around the door.
 
Dark is dark... your eyes will tell you.
If you suspect a leak, write a word on a white card and set a long exposure with a digital camera in the dark.
If you can read the word after a long exposure, it's not dark enough.
Digital cameras are sensitive to ir. A piece of paper and ink should not reflect much if any ir only visible light.
Others are likely to comment in this regard but I think this test should work.
 
You may not be able, realistically, to eliminate every tiny glimmer of light that your eye can register.

Consider it his way - if you only had the light from a few stars in your visual field, you could certainly SEE them, but how long would your film or paper have to sit before it was significantly fogged?

As others have said, the acid test is to leave some paper out for a while. My own personal test is whether or not I can see my hand in front of my face after several minutes. Not counting the 'phantom seeing' that Zuiko85 describes, which I can also attest to!

Randy

P.S. Does your enlarger have a lighted dial, or any light leakage from around negative holder? Any of that bouncing off the walls? You could really go insane. ;-(
 
Frankly, like everything else photo, this fear of not being dark enough is somewhat exaggerated, in my experience. The half covered print paper test is enough, alone with measures like taping off door seams, etc. Don't overthink it.
 
If there is any doubt ... I highly recommend one of these! :angel:

leather-lined-blindfold-400px-400px.jpg


:D
 
You must log in or register to reply here.
Back
Top Bottom