Darkening the Darkroom

Darkroom unwrapped! About 270 degrees of Ctein's darkroom, showing the plastic sheeting walls and about half of the overhead lights. No lack of lumens here.

By Ctein

As numerous recent conversations have made clear, a big darkroom concern is stray light. I concur. My dye transfer printing required me to deal with errant photons at a level that no sane process would require.

As I've made clear, I prefer black darkrooms, equipped with lots and lots of lights. You may prefer differently. Talking about what color one's darkroom walls should be, one of the commenters in a previous thread remarked that "Dave is right Ctein is wrong." Nope. Dave's right for Dave, and I'm right for me. That's all you can say. The color you paint your darkroom is as much about ergonomics as anything, and that often boils down to what's personally comfortable. For example, I could live with a grey darkroom rather than a black one, but I could never deal with one painted a bright color. It would totally mess up my color vision.

This is not just an issue for me as a color printer, it comes up when I do black-and-white work. If you're the kind of black-and-white printer who is sensitive to the tone (as in hue) of your black-and-white prints, it could very well mess up yours. Color constancy in human vision is something that is easy to upset and it can take hours to equilibrate, especially along the yellow-blue axis. I can't imagine working in a brightly colored darkroom trying to judge how warm-or cold-toned a print paper is, and whether I want to tone the processed print, and by how much. Neutral surroundings, please! Doesn't matter if they're black, white, charcoal gray, or middle gray. I just really, really want something that won't contaminate my color vision.

Be that as it may, this column's really about telling you how to find the stray light in your darkroom, not what color to paint the walls.

Step one. Turn off the lights. Sit down. Close your eyes. Meditate on how wonderful your life is for at least five minutes. Open your eyes. Do you see any light leaks? Plug them! If it's a few twinkles around window frames or joints in the wall or between the wall and the ceiling, black electricians tape works wonderfully. If it's light that's leaking around the frame of the door, put some weather stripping or flaps around the frame to baffle it. Make all that outside light go away.

Step two. Put a negative in your negative carrier, put the carrier in the enlarger, and set up the enlarger as if you were making a normal-sized print. Leaving the lens cap on the enlarger lens, turn on the enlarger and turn off the all the room lights. Once more, sit there, eyes closed, in the semi-dark and contemplate your good fortune. After five minutes open your eyes and look around the room.

Look at the light leaks from the enlarger and see where they go. Trace any patches of light on the walls light back to their sources on the enlarger head. You might have to get ingenious at blocking them. Sometimes black tape works, sometimes you'll have to build little baffles and hoods out of plastic, paper, cardboard, and tape; just do whatever it takes to trap the leakage from the enlarger. Be careful, though, not to close off ventilation ports that let cooling air into the larger head.

Pay extra special attention to any light that might be leaking down in the direction of the easel. You won't be able to get rid of all the stray light, but you'll be able to get rid of a lot of it. You'll likely have to repeat this step several times, making your modifications and checking your work, since doing the work in the dark may be difficult or even unsafe.

Test your success so far by taking a sheet of plain white paper, drawing a big fat black X on it with a wide felt tip marker, and putting the sheet of paper in your paper easel. Prepare the enlarger (and yourself) the same way you did in step two. After the obligatory contemplative five minutes, look at the paper easel. Can you see the X? You shouldn't! Or, at least, it should be nearly invisible—there should be that little light reaching your print easel.

Step three. Find a negative that has some area that is truly maximally dense. Perhaps a photograph you made where the sun is in the field of view? Doesn't matter what, so long as there's an area that is as close to D-max as possible. Got it? Put the negative in a carrier. Now, drop a bit of something totally opaque on top of the negative overlapping the D-max region. It can be a chip of cardboard, a hair, a bit of wire, anything that will make an absolutely black, sharp-edged shadow within the D-max area.

Put the negative carrier in your enlarger and focus the image sharply. Stop the lens down two or three stops to minimize flare and maximize contrast. Take a close look at the D-max area of the negative projected onto the print easel. Is the shadow of the opaque object within that area clearly much darker then the D-max of the film? If so, you're good!

If not, you'll need to figure out if it's flare or stray light within the enlarger system or light reflected off the print paper and scattered back again. A helpful diagnostic is to substantially reduce the magnification of the projected image. If you normally print 8x10, shrink the image down to 4x5 by lowering the enlarger head. That makes the projected image 3–4 times brighter, but it doesn't increase the amount of backscattered light. If the opaque shadow becomes much darker relative to the negative when you do this, then it's most likely backscatter that's causing your problem. You'll need to track that down.

If the relative clarity (or lack thereof) of the shadow in the projected image stays the same, then any problems you're having separating out tones of these dense areas are due to flare or light scattering within the enlarger head and/or the enlarger lens. You'll have to figure out what to do about that, but at least you'll know the problem isn't your darkroom.

Ctein

Ctein's regular weekly column appears every Thursday morning, for some value of "morning." (Note time stamp on this week's column!)

Comments

[Pak]

Hi Ctein,

Thanks for a great article which is incredibly informative and practical. I'm still learning darkroom technique, but you've opened my eyes up to a couple of potential problems that I may have to rectify... Or perhaps "optimise" -- given that my work space (and wife) dictates: bathroom first, darkroom second.

I'm not sure if anyone reading this will think you're paranoid or OTT, but certainly from what I can imagine these measures are appropriately sound. I only wish that I had the time and space to dedicate to a room like you have. I suspect there is a lot more tinkering that you've done in that photo to optimise the end result and I for one hope you will share it here.

Cheers, Pak

[richard]

Just curious, but I've always found keeping my eyes open for five minutes is the way to detect stray light. I might be odd though...

[Mike Johnston]

Richard,
No, it's much more effective to keep your eyes shut for five minutes. (Of course you do have to open them AFTER that time. Duh.) It's an effective shortcut. It will take a considerably longer time to see and identify small, faint light leaks if you sit there with your eyes open. Close your eyes for a while and the light leaks will pop out at you once you open your eyes again.

Mike

[hugh crawford]

In grad school there was a guy who had something like a compendium lens hood on his color enlarger. The enlarger belonged to the school and they weren't keen on him rebuilding it's stage and bellows or repainting the darkroom.

[robert e]

A bit off topic, and just out of curiosity, but whenever I see glossy plastic blackout sheeting, I wonder whether specular reflections off glossy walls are a cause for concern in a darkroom. (I assume not, if it's good enough for Ctein).

[Steve G, Mendocino]

Ctein:

Let's hear it for black plastic sheeting! Years ago I built a 'darktent' in a garage with the stuff. Simply quartered the garage with 2 lengths of iron clothesline wire tightened with turnbuckles. Stapled black plastic sheeting to 2 walls and draped and taped it over the top and sides to form the 'room.' Simple, took less than a day, and cheap. Lasted as long as I lived in that house.

[Eric Rose]

Well if you get tired of printing in that area you could always make a grow-op out of it LOL.

[Patrick Dodds]

That is one frightening looking room Ctein - an architectural gimp mask - though it looks like you can really set to your developing in there.

[Mike]

The room looks quite scifi actually - that sort of seem appropriate

Great info Ctein, even though you've sworn off film for the future!

Mike

[Philip Morgan]

I also have gone to some lengths to reduce enlarging flare in my darkroom: http://www.philipmorgan.net/2009/01/05/reducing-enlarging-flare/

I believe my prints have improved as a result.

[richard]

Re eyes-wide-shut-or-open. Thanks for the advice MIke. I suppose I was talking about ambient light which, rightly or wrongly I tend to worry about more - but then I only use the "darkroom" for film loading/unloading - and it takes me hours to load sheet film.

[Dennis Ng]

For the wall part, I just bought a small apartment to be my Dark Apartment as my dear think that my 3 Jobos have outgrown the toilet by a lot . As I am doing my planning, I wonder it would be better to get the Nova Darkroom tent (which will fill up nearly the whole living room, that is a very small apartment) or I should go to the darkroom "painting" like Ctein. Cleaning and later small insert would be an issue I think. I am not comfortable with that darkness :-). Like white wall.

For the enlarger, I have done the first issue of enlarger light leak, but never thought of the second or third issue. How to fix the paper backscattering and enlarger lens issue? For 4x5, I enlarge and for 8x10, I contact print. Any difference of the strategy of fixing these two issues.

[Mike Johnston]

Richard,
I don't know whether this pertains to you at all, so please forgive me if this is useless information.

With some students I found that they actually do better in pitch dark doing dexterity tasks such as loading film if they do shut their eyes. Some people seem to have a hard time "relaxing" their eyes in the dark, and continue to strain to see even if they can't. Anxiety about light leaks might be making things worse. Try closing your eyes and purposely relaxing, and concentrate on visualizing what your hands are doing.

Again, no idea if this pertains--just throwing it out there in case it might be helpful.

Mike

[ctein]

Dear Robert,

Actually, less of a concern than flat black. Flat black scatters a small amount of light in all directions. Shiny black reflects most of the light at the complementary angle to the angle of incidence. Unless you had everything in your darkroom are arranged just so (wrong), light emanating from the enlarger just bounces around the room several times until it's fully absorbed; very little of it gets scattered back in the direction of the print easel.

If you ever need to make any REALLY black target, take a sheet of shiny black material, roll it into a cone and curve it a little bit so it's more like a horn shape. Put a card over the opening with hole in it about about half the diameter of the cone. Light goes in but it won't come out!

~~~~~~~~

Dear Steve,

As I've mentioned in comments previously, this darkroom was thrown up as a temporary measure when I moved into this house, in a matter of days, using black plastic stapled to both sides of a 2 x 4 frame, adding a door purchased at the local hardware store. The temporary measure has lasted 25 years now; I am certain it's going to last me until I tear down the darkroom.

~~~~~~~~

Dear Patrick,

You're being fooled by the distortions caused by a wraparound panorama made standing in the middle of the room, combined with an absence of scale. Those trays sitting on the tables on the opposite side of the room? They are 17" x 21" trays; it's a large darkroom!

Mike has been in it; he can confirm that it is spacious and well laid out.

~ pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
======================================
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 
======================================

[Alex Vesey]

Dear Ctein,
Interesting article. I doubt I will ever had room for a set up like this, but it does look enticing--a world for yourself.

How do you handle ventilation? And do you keep the black bags up all the time? I some climates, one will get yicky mold build up between the bags and the wall.

Alex

[Jeff Damron]

I don't care what color anybody's darkroom is - I'm just happy to see Mike and Ctein talking about darkrooms. Again.

[Christopher Lane]

Has Ctein thrown down the gauntlet?

[Isaac Crawford]

Ahhh, plastic sheeting. I once had an attic apartment. I wanted to do some printing but the bathroom just wasn't going to accommodate my Omega 4x5 enlarger. So I put it in the next room and used the bathroom for the wet stuff. I had a total of 4 windows, so I just blacked out the whole place, my entire apartment was my darkroom! It worked fine as a darkroom, but I had a few other issues. First off, I did a little too good a job with sealing the windows, I noticed a distinct lack of ventilation. Secondly, it was rather disconcerting to wake up and have zero clue as to what time it was. When I looked at my alarm clock, I had no idea if the time was AM or PM...

I once worked in a slide duping lab (try to find one of those now!) and made myself a little space to do some enlarging on the side. The boss liked what he saw and started to offer slide enlargements. I learned a hard lesson in controlling light spilling from the enlargers. E-6 took about 45 minutes to process and dry. It was absolute torture to make a test only to find that light leaks made the enlargement worthless. We ended up making black baffles that dropped down past the negative stage and of course painting the walls near the enlarger a matte black. Luckily, duping film was pretty slow, so we didn't have to go to the lengths that some others might have had to...

[Richard]

Mike

"With some students I found that they actually do better in pitch dark doing dexterity tasks such as loading film if they do shut their eyes."

Now that is rather interesting. When I think about it there is an element of "trying to see in the dark". The brain is a funny thing. I'm going to give it a try.

Cheers

[Dave]

Ctein - "Dave's right for Dave..."

Are you sure about that?

[Roberto C.]

What I liked most of all the discussion is the DIY black body suggested by Ctein in one of his comments.

R.

[Tomas]

Let's hear it for black plastic! I too am using a dedicated room for a darkroom; I made timber frames and stapled plastic to them. I can easily remove the frames when we move (since we are currently renting).

I hadn't considered stray light from the enlarger - I have a Beseler 45 somthing or other (not near me right now) - and there is light escaping from the top half. I hadn't thought to try and contain that since it didn't seem to reach the easel. Although now that you mention the X trick, I'm thinking I should make sure everything is ok...

[Frank]

I don't want to be around when fire breaks out, with all that plastic, and tape and other flamable stuff. Not to mention the dust and smell .. I worked in darkrooms for years, pure horror is that Ctein stuff ..

[Hélcio J. Tagliolatto]

Mike and Ctein! (and David Vestal, Gordon Lewis, Anchell, Fuller, Dr. Chapman, Weese and others....) I've a debt of gratitude to all of you.
In the times before Internet (and living in the Amazon) your writings, texts and advices were the only source for serious photography, all written with a touch of class.

[Don Parsons]

Looks like the bat cave! :-)

[Carl L]

My formula for light leaks is. Expose photo paper a little, no neg in enlarger, so you get the latent image over the hump.
cut paper up into small sizes--put them in different places in darkroom, with coin in middle. 10 to 15 mins should do it--keep safe lights on. develop--if you can see the coin imprint. you have a problem some where.
Also check light leaks from enlarger.

[skink74]

As my darkroom isn't permanent and I have to put up and take down the lightproofing, electrical tape wouldn't work for me. to cover cracks around doors/windows I use 120 backing paper.

[Sevad]

"Actually, less of a concern than flat black. Flat black scatters a small amount of light in all directions. Shiny black reflects most of the light at the complementary angle to the angle of incidence."

Makes you wonder why camera and lens makers went to the bother of making lens hoods and the inside of cameras flat black when they could just have left them shiny...

[ctein]

Dear Sevad,

Heh, thought someone would ask about that. Good question! Here's the good answer:

There are two reasons why shiny black paint would create real problems. The first is that the light coming in is strongly directional, headed towards the film/sensor, and the walls of the camera and lenses and hoods are parallel to that direction. Light that hits them and gets specularly reflected is going to continue on more or less the same path that it had before, towards the film.

The second problem is that specular reflections preserve the pattern of the light hitting the surface. Why, you might even say they "mirror" it [vbg]. The lens is filled with glass elements that create images. This is not a good combination. Think of what happens when you point the camera directly at a bright light source, so that even the very faint reflections from the shiny smooth lens surfaces become visible. All those ghost images! That's what would happen if you painted the interiors shiny black instead of matte black. Shiny may work better for suppressing light but matte produces a diffuse glow that doesn't show up as distracting ghosts.

Now, here's something you may not know. Neither matte nor shiny black paint work very well! That's because a large fraction of the incoming light rays are almost parallel to the surfaces when they hit them, what we call grazing incidence. Every flat surface is very reflective at grazing incidence, whether it's painted shiny or matte. To see that for yourself, find a piece of matte black cardboard or a matte surface inkjet print, hold it up horizontal just below eye level and look at the surface as you orient yourself towards a light source like a window. Look at how bright the reflections are from that matte black paper at grazing incidence. It's not very black when there's parallel light bouncing off of parallel surfaces. the same problem exists in your camera gear.

Here are two tricks that manufacturers use to suppress that light. One is to use aperture stops within the lens. If you've ever taken apart a lens, you may run across designs where there is a flat metal plate with a circular hole in it immediately before or after some lens element. The holes are smaller than the lens elements, so the full diameter of the element isn't being used. You may have even wondered why they didn't save money and weight by making the lens element and the barrel smaller instead of "throwing away" part of the aperture. Well, one reason for doing that is to make sure that there are no light rays at the very edges of the lens elements near the lens barrel, where they could be reflected.

The second trick is far more common. The manufacturers rib those matte black surfaces. Look inside a well-made lens hood, lens, or camera body, and you'll see that the walls aren't flat, they are grooved. Those grooves catch the light. If you're looking through the equipment from the point of view of the film/sensor, the "front" sides of the ribs are the ones facing the incoming light, but you mostly can't see them. The sides of the grooves you see are the back sides, which are shadowed. Light hitting those surfaces tends to get bounced forward, not back. What reflections you see are from the edges of the grooves (which aren't perfectly thin) and from light that gets reflected twice, once from the front surfaces of grooves and then again from the back surfaces of adjacent grooves.

And that is today's expository lump! I hope you found it, umm, enlightening.

~ pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
======================================
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 
======================================

[robert e]

Dear Ctein,

Thank you for some very illuminating reflections on reflections. And a big extra thanks for tossing in the Cone of Darkness. What a cool bonus!

robert e