Pinhole Camera II: The Daa-a-a-ark Room

In the last post I showed the simple pinhole camera I've made. Very basic, very easy to use - except that you have to load the photo paper in a darkroom and you have to develop it yourself.

A darkroom isn't complicated. It's a room with absolutely no light coming in from the outside. It's not necessarily dark, though; unlike film, paper is not sensitive to red light, so you don't have to be in darkness. A "safelight" that emits red light, and only red light, will let you see what you're doing - you can actually see the image appear on the paper when you develop, which is really cool.

To develop the paper you need three trays for developer, stop (not really necessary) and fixer. A few darkroom tongs are cheap and a good idea since you don't want to get smelly chemicals on your fingers, or accidentally mix them. If you develop your own film you can use the same stop bath (if you use that) and fixer you already have. And if you're just playing around you don't need to be very careful with temperature or time, so a thermometer or clock isn't all that critical. You can see the paper develop so just stop when the image starts looking really dark and solid.

What about developer? Normally you would use special paper developer for photo paper, rather than film developer. Paper developer is a lot more active, giving you good contrast prints, and is incidentally a lot cheaper too. You can use film developer for paper, but it's much slower and will apparently give you low contrast, washed-out looking prints.

But this only applies for printing from a negative. A film negative is low contrast - the difference between the darkest and lightest areas isn't that large. But here we use paper as the negative. We're exposing the real world on the paper, not a low-contrast negative. And the real world is usually really contrasty, with huge light difference between the darkest and brightest areas. So as it turns out, film developer is a decent match for this use, and results in fairly good paper negatives.

Safelight

A safelight is not strictly necessary, but it'd really suck to have to do everything in pitch blackness. Safelights - light fixtures with a dark red glass front - are available but they're fairly expensive. Safelight red bulbs that you can use in normal sockets are not cheap either and don't last forever. People warn against using cheap red "party" lightbulbs. There's no guarantee they really cut out all unwanted colors, and edges and scratches may be uncovered by the red paint.

Lightbulbs are hot, need mains power and waste a lot of energy, and they're gradually disappearing the world over. The new hot item here is LED lighting, with many manufacturers pushing LED bulbs. Long before the advent of the white LED's that's made this lighting revolution possible we've had red LED's used in all kind of electronics. A red LED is cheap, will only emit light in fairly specific frequencies, can run on low power and lasts almost forever. Perfect.

My first idea was to get an LED bicycle light. But since I can never have too much complications in my life I decided to go for a more DIY solution. In an electronics store I found an LED "brakelight" kit for car rear brake lights, with a circuit board and male socket. I got the kit, a dozen red 1W LED's, a matching female socket¹ and a light switch. For power I used an 12v transformer I had lying around.

To keep with a filmy theme I attached the socket to a 35mm film canister, with the cable going through the lid. A second white film canister fits nicely over the light itself and serves as a diffuser. I hang it in the bathroom simply by wrapping the cord twice around the curtain rod over the bathtub. The light is plenty strong - so strong that I hang a towel over it to dampen it a little - and seems to be completely safe for the paper as far as I can tell.

 

Here's the safelight disassembled. I've soldered the LED's and other components (just a diode and a resistor - it really is very simple), attached it to the socket, attached the male socket to the base canister and done the cabling. Works very nicely.

Making our bathroom really dark turned out to be the most complicated part of this - much more so than making and using the pinhole camera. The room has to be really dark - any stray light from outside will ruin the paper. I tried an elaborate idea with light-proof curtain fabric and a frame made of PVC tubing that utterly failed - on the positive side I now have several meters of tubes and connectors to use for something else. I finally just taped the fabric over our bathroom door (What would I do without gaffer's tape?²). I also close the doors to the washroom outside, making doubly sure I won't have any unwanted light seeping in. Seems to work, if not all that practical.

Here's the darkroom, in color and converted to BW (click to enlarge). There's plenty of space, running water and efficient ventilation, and I get a good-sized workbench simply by using the bathtub covers. If I ever get an enlarger I can place it along the wall out of the picture on the right.

This kind of picture, incidentally, is a perfect task for a digital camera. The light is nearly monochromatic, and getting the exposure right without trial and error is almost hopeless. Had I tried to take this on film for whatever reason I'd had to take a whole roll and probably still not get an image I was happy with.

I've taken two pictures with the pinhole camera so far - you don't get much of a frame rate when you have to return and develop each image before loading the next. I used 13x18 cm Fuji multigrade RC paper, the cheapest one in the local shop. The pinhole exposure calculator specified 1.5 minutes for hazy sunshine but that seems a little short, and even two minutes was not really enough. I'll try three minutes next time.

The lack of red sensitivity means the images become just a little odd - blue skies go very bright while reddish objects, like brick buildings, become dark. The long exposure time means that anything moving, like people, disappear completely. And there is of course no way to judge the composition; you find out what you got in the frame only when you develop the negative.

The first shot, my standard view out from our balcony. I actually got a bit of motion blur here since the box shifted a little halfway through the exposure. But the tonality is nice, and evokes an old-time photography (the lack of red sensitivity is probably the reason; really old films were not red-sensitive either). I especially like the mottled sky that really exaggerates the haziness.

The second shot, with an unfortunate "composition malfunction". I wanted to have the bikes near the bottom with the skyline breaking into the top near the right end. But the wall I used for support apparently sloped a bit without me noticing so instead you get this inspirational study of an Osaka sidewalk. This was stable, and there's more detail than in the first shot; notice that the wheel spokes are clearly visible in the closer bikes, for instance. At the very top you can see how the red traffic signs have turned black. This is a busy sidewalk, by the way, with lots of people passing by, but with two minute exposure there's not even a hint of people in the image.

What's next? I think I'll take a few more shots with this camera but it's not very practical of course. I got lucky recently and found some 4x5 format film holders in decent condition for cheap in a camera store. So I'll build a more solid camera that can fit a film holder; that way I can bring and shoot several exposures before I have to develop them again. And perhaps, instead of a pinhole I'll try using a lens. Even a very simple glass lens is a real improvement on a pinhole, with more detail and much faster exposure. Of course, then we'll have to start worrying about whether and how to focus, and shutter speeds may get too fast to do manually. But those are problems to solve later.

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#1 That way I'll save literally minutes of time switching the LED lamp when the this one breaks some forty years from now. How's that for optimizing my time?

#2 I'd have to make things properly instead, I guess, instead of cobbling stuff together with tape.

Pinhole Time

Feeling Negative is a fun new site for film photography enthusiasts, and I can warmly recommend it. They have started a series on DIY large format photography, beginning with a simple pinhole camera and using photo paper for a negative. That has inspired me to try making my own.

A pinhole camera is by far the simplest camera possible. You have a light-proof box with a piece of film, a sensor or a retina on one side, and a small hole (a "pinhole") on the other. No lens, no focusing (everything is equally in focus) and no mechanics beyond a way to cover and expose the hole. In evolution it's an intermediate stage between having a light-sensitive patch and an eye with a lens; the Nautilus is a group of animals that just kept the pinhole eye and never so far developed a lens.

The way a pinhole works is very simple: imagine that you're a spot on the film or a pixel on the sensor. Everything is dark, except for the light from the hole. That light comes from whatever is visible through the hole, so with a smaller hole you'll see a smaller part of the world. Make the hole small enough and each part of the film will get the light only from a tiny spot, making a recognizable picture. Of course, the smaller the hole, the less light you get, so exposure time also gets longer and longer.

If you are nearsighted you can see the effect of a pinhole directly. Remove your glasses, and curl your index finger and thumb so you get a tiny hole in the middle. Put your hand right up to your eye so you see through that hole. As you squeeze your finger the hole will get smaller and you'll see that the image gets much sharper but dimmer¹.

You'd think you could make the image as sharp as you like simply by making the hole smaller (and accepting the longer exposure times). That's not possible, unfortunately. Because of diffraction the image will start becoming blurrier again as you keep making the hole smaller. There's an optimal size for the hole that depends on the focal length - the distance between the hole and the film - of the camera. How do you find out the best pinhole size? The easiest way is to use an online calculator such as this one.

My pinhole camera is using 13×18cm photo paper as the film. Why that size? It's small enough to be cheap (a box of 50 sheets costs just a few hundred yen) and still large enough to make a good sized, easy to scan negative. After a bit of rummaging I found a suitable cardboard box with a short side of about 17 cm; that makes for a pleasant, somewhat wide angle of view with this paper. The pinhole calculator tells me that I need a pinhole slightly less than 0.5mm diameter, that it corresponds to an f-stop of around f/350, and that exposure time in clear daylight will be about a minute and a half.

There's several ways to make the actual pinhole. Ideally it should be made in a thin, rigid material, be nearly round and not have rough edges. A good choice is an empty aluminum can - cut out a square from a can, flatten it, then make the hole. I made a small dent in the aluminum with a pen, then used a sharp tool (needle-nose tweezers) to slowly drill a hole in the middle of the dent from both sides. 0.5mm is fairly big, so it was easy to check the size with calipers and a loupe.

Large-format pinhole camera. Note the high-quality cardboard, metal from a can of real beer (not cheap happōshu) for the pinhole and the exclusive gaffer's tape trimmings to give it that refined air of executive class - only the very best materials is good enough for us here.

The box is simplicity itself. I light-proofed it by liberal use of gaffer's tape along all edges, and the pinhole plate is taped in front of a hole in the center of the box. Another piece of tape with an edge folded in serves as the shutter - pull the tape to open, then attach it to close again. With a shutter speed in minutes, a few seconds doesn't matter. I cut a flap on the back, taped the edges, then added strips of tape along the flap to close it. The tape along the edges makes sure the flap tape doesn't stick to the cardboard. That way I can open it without ruining the box. The "film holder" is four bits of blue-tack to hold the paper in place. The whole construction, pinhole and all, took perhaps half an hour or so.

The camera from he back. Stick the photo paper to the four lumps of blue-tack, close the flap and seal it with the strips of tape. The blue-tack clings to the paper, unfortunately, but it doesn't seem to affect development. Still, a better way to hold the paper is probably a good idea.

To use the camera you put a sheet of photo paper in the back and close both back and pinhole. Place the camera where you want to take a picture - make sure it's stable - open the tape shutter, wait two minutes or so, tape up the pinhole, then return home. Take out the photo paper and develop it much like you would with film (developer, wash, fixer, wash again, then dry).

Now, the paper is light sensitive. That's why you can use it to capture images after all. Film comes in light-tight rolls or in small canisters and you develop them in special lightproof tanks. But the paper is a bunch of sheets in a box. How do you get the paper into the camera, and how do you get it developed? You need a darkroom. This is getting pretty long already, so I'll talk about that - and show the results - in the next post.

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#1 If you're not nearsighted you'll just have to take my word that it works. Don't complain - you don't know how good you have it.