I was recently asked for advice on pinhole cameras by a flickr contact who had seen some of the results from my homemade efforts. I ended up writing a fairly long e-mail reply, which seemed like it ought be tidied up and shared somewhere. So here it is.
Now, pinholes – where to start…? Best make yourself a coffee then sit down by a warm fire with this lot. Mine have gradually evolved with experience, so hopefully I can give you a few hints. It’s probably worth looking through the Homemade Pinhole
flickr pool and discussions for ideas, and help too.
Obviously, the basic requirement is a lightproof box, so any reasonably thick cardboard will do. If you’re going to use photographic paper or sheet film then things are pretty easy, you just need to make a shutter of some sort and add a pinhole. Then take a box the size you want, cut a hole in the center of one side and stick the shutter/pinhole over it. My latest shutters copy this basic sort of design, as a lever action like that is much quicker to open and close than a flap or a slider. I use black mount board offcuts to make them mostly.
The pinholes themselves need to be in a material that is stiff, but as thin as possible. Kitchen foil isn’t really up to it. I use a piece cut from a beer can, hammer a small dent in it and sand it down with an emery board. Repeat, until you have a nice thin area, then you can poke it carefully with the tip of a tiny needle to make the hole. Google will turn up a number of proper explanations that will probably make more sense than this and have illustrations to back them up. To measure the pinhole diameter, the usual method is to scan it at a known resolution and measure the width in pixels and do the sums.
So for a sheet type photographic medium you’d be all set: put film/paper in box (holding it in place with paperclips, blutac or something), close box, point, open shutter. The drawback with this is that you’ve only got a one shot camera, unless you lug around a changing bag or equivalent to reload. So that brings us on to roll film, which is where it gets complicated.
The complications in using roll film of any kind – I say any, but basically we’re talking 135 or 120 format – arise from the need to keep the box light proof, but be able to wind on the film, and also keep the film flat across the image plane. This is what has given me the most grief in all my efforts.
For 35mm you have the advantage that it comes in a lightproof container to start with, so you can construct a lightproof box with a pinhole at one end, and at the other make slots on opposite sides just big enough for the light trap of a 35mm can to fit into. You need a full film and an empty one. Feed the leader through the slot and tape it to the spool of the empty one, Then take up the slack fit the cans snugly in the slots, bodging all the gaps with black tape. You then wind from one can to the other, and when it’s finished, either wind all the way back or just cut it and wind on. Another bonus of using 35mm is that you can make pretty tiny cameras.
The disadvantages of 35mm are that the film size isn’t great for pinhole type levels of sharpness, and having to work out how much to wind on to avoid overlapping frames. For the latter you need some sort of clicker so you can count sprocket holes – 8 clicks = one 24x36mm frame, 16 gives you a 72mm long pano frame, 18 to a roll, 6 would be about right for a 24mm square frame. I use a small strip of film, folded over and taped so that it will stick into the holes. It’s stiff enough to make an audible click but bendy enough to not damage the film. The other technique I’ve seen is to use a bit from a plastic spiral binder thingy (see this topic
for various links).
If you use 120, the bigger frame size gives you a better (relatively) image quality. Another large advantage is the presence of frame numbers on the backing paper, that let you easily get the spacing right for 6×4.5, 6×6, and 6×9, or by counting alternate numbers, anything up to 6×14. The problem, is finding a way to wind the film on, without making too big a hole in the box, and while still being able to load and unload.
I’ve ended up using short lengths of bolts with a flat piece of beer can glued into a notch on the end to fit into the ends of the spools, which is hard to explain in words.
As far as construction materials go, I stopped using cardboard (except for really small cameras
) because I found either it’s not stiff enough, or you can’t cut it very precisely. Foam board is much better, you can cut it really easily and make nice stiff boxes. I stick it together either with copydex or a gluegun, depending on the joint. You can either use the black foam board (which is a bit more expensive, or spray white foamboard black. The beauty of foamboard also lies in the fact that it’s exactly 5mm thick, so it makes square joints very easy and makes calculations a bit easier. Because the white stuff is not completely opaque I paste 120 backing paper all over the outside of the camera and overlapping any bits that open.
So if you’re going to build from scratch what I’d suggest is think about what size frame you want. This little program
is useful, as it can calculate the diagonal field of view for a given frame size/pinhole distance, and tell you optimum pinhole size, f-number, and calculate an exposure chart (even including reciprocity failure for some films). Just be aware that with a short distance, you get a wide fov, but the edges end up very underexposed. There are two reasons for this. If you look at my Rose Bowl pinholes
for example the distance from pinhole to film is 30mm at the centre of the frame, but more like 60 at the edges, so that’s at least 2 stops difference. But also at extreme angles the pinhole becomes more and more foreshortened so that the effective area is reduced by at least the same. Which is why I never really filled the 6×12 frame with that camera.
One way to deal with this is to curve the film around the pinhole like my other camera.
It certainly helps, but really is a pain, so I wouldn’t recommend it for your first effort. It also makes for a much larger camera.
Once you have the frame size and pinhole distance, you can design the rest of the camera around that. the way I do it is to imagine a simple box made from two rectangles the same size as the frame separated by the pinhole to film distance. then I add enough space on each side for the film spools, and go from there. I draw it full size on 5mm squared paper, then I can lay the foamboard and film spools on the plan and workout how it’s going to fit together. I usually find as I build it I hit a snag I hadn’t thought of, so you have to be ready to improvise.
It’s also worth taking a moment to think about how you’re going to use it, physically. You’re going to be using exposure times of a few seconds upwards as far as half an hour or more, so you need to keep it still. I have cannibalized the tripod mounts from a old camera cases and glued them on the bottom, so I can fix it to any old tripod, but a decent elastic band might do just as well. (Incidentally to make sure the camera is firmly closed a couple of decent sized elastic bands are just right.) Bear in mind that long exposure times are necessary if you’re going to get the exposure roughly correct. If you use ultra fast film, and end up with exposures of 1/2s it’s hard to get that right. It’s much easier to time 10 seconds, and less of a problem if you’re half a second out. Fast film also fogs more easily.
Hopefully this doesn’t make it all seem too daunting. It shouldn’t be – it’s really pretty simple, and even the most basic pinhole camera will produce a picture. But the more thought you put in to the build, the better the camera is to use, and keep using – just like any other camera.