Stenopeika recently launched their Air Force 11x14, billed as the most affordable ultra large format camera in the world. Samuele is not wrong on that. It is also still well beyond what I can spend right now.
So I built one out of a cardboard box. Twelve by sixteen inches of negative real estate, total cost under £10, and the results are good enough that I am genuinely keeping it as a working camera rather than just a curiosity. This is the build, the maths, the four trips to a graveyard to get a usable frame, and what I learned that has now made me want to build something properly using the same principles.
If you have followed the black and white paper reversal work I have been doing recently, this is the next step in that journey: doing it properly big.
Why I wanted to build it
The reversal work has been giving me lovely little positive images straight out of the camera. The catch: they are little. For the first time in my photographic life I started yearning for a bigger format. I wanted 8x10 paper reversal images.
So my brain started chewing on the problem. I cannot afford an 8x10 camera. Could I 3D print one? The body, maybe. But then the bellows become a problem (proper bellows are £200 and up), and the focus mechanism, and the lens board. The cost piles up fast even before you have something working.
Could I make a pinhole camera instead? Pinhole removes the lens, the focus, the bellows. Just a box, a tiny hole, and a piece of paper. Suddenly the problem becomes much simpler. A box made of wood, perhaps. Then I caught myself: why does it need to be wood? It just needs to be light-tight and hold its shape.
A cardboard box would do.
Then the second realisation. If I am making the box myself, why stop at 8x10? Whatever size paper I can buy, I can build a box to fit. The most easily available large paper I could find was Ilford Multigrade RC at 12 by 16 inches. That is properly big. Big enough to satisfy the yearning.
So that is the build target: a 12x16 cardboard box pinhole camera, using Ilford MG RC paper, reversal processed to produce positive prints straight out of the camera.
The maths
Pinhole cameras have a sweet spot for the relationship between the size of the hole, the distance from hole to film, and the resulting sharpness. Make the hole too small, diffraction blurs the image. Too big and you lose sharpness because the hole acts more like a window than a lens.
The website I always use for this is mrpinhole.com, which has a calculator that gives you the optimal hole diameter for any given focal length (the distance from hole to film/paper in a pinhole camera).
My box was approximately 300mm deep, which the calculator told me wanted a pinhole around 0.6mm in diameter. Two checks needed:
Image circle. I needed to make sure the pinhole’s coverage would be big enough for the 12x16 paper. A bit of Pythagoras gave me a corner-to-corner diagonal of around 507mm. Some allowance for tolerance and the pinhole I was building would project an image circle of roughly 530mm. Comfortably big enough for the paper.
Angle of view. With those dimensions, the camera would have an angle of view somewhere between 80 and 90 degrees. Very wide. Wider than I would normally choose, but interesting.
That gave me everything I needed to build.
The build
Step by step. None of this is difficult. Total spent: under £10 for the box (free, found one), paint, tape, magnets, and a tiny piece of brass shim.
1. Paint the inside black. Any internal reflection ruins the image. Matt black paint on every surface inside the box. Standard pinhole/camera obscura practice.
2. Make the pinhole. Drilled a 0.6mm hole in a small piece of brass shim using a 0.6mm Dremel-style drill bit. The brass is the actual aperture; the box is just the housing.
3. Make a lens board with magnetic shutter. This is the technique I used on my proper large format pinhole work. Mount the brass pinhole on a small board, and put a separate steel plate behind it with magnets, padded so it sits flush. The plate becomes a clip-on shutter: pull it off to expose, snap it back on to end the exposure. Quick, repeatable, no shake.
4. Cut a hole in the box the right size for the lens board, glue the board on, position the pinhole exactly central.
5. Mark the paper position inside the box. I worked out where a 12x16 sheet would sit on the back wall, marked the corners. Because of my box’s exact dimensions, I would not actually get full 12 inches of height. I would get 11 by 16. Close enough. Not worth rebuilding the box for the missing inch.
6. Light-proof everything. A test seal showed light leaking through one corner of the box. Sealed with more black paint and tape. For the final shoots I also draped a heavy black towel over the whole thing once loaded, belt and braces.
7. Loading mechanism. This is the awkward bit. The box is sealed at the front (lens board) and the back (where the paper goes). To load paper, you have to open the box. To open the box, you have to break the seal. My solution: cut the tape sealing the box, load paper using double-sided tape to stick it to the back wall, re-seal with fresh gaffer tape. After each exposure, cut the tape carefully so as not to destroy the cardboard. Old tape stays on, which helps with the light-proofing of the next exposure. Iterative process.
For the final version (the wooden portrait box that this build is pushing me toward), I want a proper hinged lid. The cardboard is fine for proving the concept, but the tape-cutting process is genuinely the limiting factor on how many exposures you can do in a session.
![PLACEHOLDER: the finished cardboard box pinhole camera, showing the lens board with the magnetic shutter clip on the front]
The exposure problem
A pinhole at f/410 (calculated from my 0.6mm aperture at 300mm focal length) with paper at an effective ISO of around 2 means very long exposures. The Sekonic L-308 meter could not even calculate the exposure. It went off the bottom of its scale. The Reveni Labs spot meter could, just about.
A typical exposure was suggesting 40 minutes for a building in shade, 4 minutes for the sky. Those are not typos. Genuinely minutes of exposure for a single frame.
This is the practical reality of ultra large format paper reversal. You make one exposure per scene, with significant downtime between exposures. It is contemplative photography by force, not by choice. If you want to shoot fast, this is the wrong tool.
It also means you cannot photograph anything that moves. Which is the bit that ultimately pushes me toward the wooden portrait box I am planning next, because I want to do portraits with this process, and even the most patient model is not going to hold still for 12 minutes.
But for buildings, landscapes, sky, anything that does not move, the long exposure is workable. You just plan around it.
The shoots
Four trips. The first two in my backyard for testing. The next two in a local graveyard, which has the advantage of being properly atmospheric and having tall stone buildings to point the camera at.
Test 1, backyard. First exposure ever from the camera. Twelve minutes of exposure on an 8x10 sheet (I was not going to waste a 16x12 on the first test). Underexposed but workable. Got an image. The camera works.
Test 2, backyard with 16x12 paper. Fifteen minutes. Also underexposed. Starting to understand that paper reversal at this scale wants substantially longer exposures than I am intuitively reaching for.
Test 3, graveyard, evening. A proper composition with a foreground gravestone silhouetted against the sky, which I had realised in the car was the right approach: rather than fighting the contrast between a lit building and a properly exposed sky, use the foreground as silhouette. Half an hour of exposure as the light dropped. Came home, developed it, and it was still underexposed. Genuinely disappointing.
Test 4, graveyard, daylight, thin haze. Twelve minutes on a flatter-lit foreground composition with the sun behind me. Came back, developed it, and it worked. A proper 11x16 positive image straight out of the cardboard box.
![PLACEHOLDER: the successful 11x16 graveyard frame, showing the foreground gravestones and the sky from the cardboard box camera]
What worked, and what I learned
The pinhole was sharper than I expected. Not lens-sharp, obviously, but distinctly more crisp than the lo-fi pinhole aesthetic I was bracing for. The 0.6mm hole at 300mm gives you something genuinely workable.
The reversal process produced lovely contrast. Punchy blacks, decent tonal range in the highlights, the kind of slightly graphic feel that paper reversal does well at this scale. The size adds presence.
Composition with foreground is essential. Trying to capture lit landscape and sky in the same frame is a losing battle at these exposure times. By the time you have given the shadowed foreground enough light, the sky is blown out, and the clouds will have moved anyway over a 10-15 minute exposure. The silhouette-against-sky approach is the answer.
The shutter works. The magnetic clip system worked exactly as designed. No camera shake, no light leaks during the swap, easy to operate.
The cardboard is genuinely limiting. The box flexes in the wind. It is not robust to repeated openings for loading. The tape-cutting routine is slow. The whole thing is one wet day from being unusable.
So this is a prototype
That last point is the important one. The build worked, the camera works, I am keeping it. But I have learned what I would want to do differently if I built it properly, and there is enough of a real photographic appetite here to justify the better version.
The next build (already underway) is the wooden portrait box: same principles, but with a proper lens (an Emil Busch Aplanat I have been cleaning up) instead of a pinhole, a fixed focal length sized for portraiture, a hinged lid for loading, and a build solid enough to last. Exposure times will drop dramatically (from 12 minutes to maybe a second or two with a proper lens at f/6.3 or so), which puts portraiture back on the table.
The cardboard box is what taught me I wanted to build that camera. It is a prototype that justified the next step. And it cost about £10. You can read about the wooden ULF box camera build here, which is where this whole journey ended up.
For anyone curious about ultra large format without spending money on a “real” camera: build a cardboard box pinhole. Make the box, paint it black, drill a tiny hole, and load it with the biggest paper you can get hold of. You will spend less than £10, take longer exposures than you would believe necessary, and end up with positive images bigger than most people have ever seen come out of a camera. Worth doing.
The costs
For anyone wanting to attempt this:
Ilford Multigrade RC 16x12, pack of ten: around £38, which works out to £3.80 per sheet.
Chemicals for the reversal process: roughly £1 per 16x12 sheet, using the Stenopeika BWPrev kit (links in the video description).
Brass shim, magnets, paint, tape: a few pounds if you don’t already have them, free if you do.
The box: free.
Per-frame cost is about £5. Per-camera cost is essentially zero. For ultra large format imaging, you will not beat that anywhere.
And if you want to skip the DIY entirely and buy a proper ULF camera, the Stenopeika Air Force 11x14 is the genuinely most affordable option I am aware of. Samuele’s claim holds up.