Building an Instant Film Pinhole

I built this instant film pinhole camera last night. The process took about three hours from start to finish.

While this isn't a real step-by-step, here's how I did it. Please realize, nothing in this is 100% accurate, which suits me just fine. It's part of what I love about pinhole photography.

List of materials/tools:

• A Polaroid CB-103 film processing unit (more about that later) 
• Foam core board (like poster board, only much thicker); most drug and grocery stores carry it for about $5 a sheet, which can make several cameras
• A razor blade knife; I use an xacto-style knife, available at hardware and craft stores for about $5
• Gaffers tape; in my experience I've found this tape, which is expensive (about $20 a roll) is the best at making cameras; a single roll will last a very long time
• Flat black paint (only if the foam core is a color other than black); cheap is fine, I found a can at Home Depot for about 99 cents
• A ruler; I prefer to measure in millimeters for better accuracy
• A pen
• A pinhole; this "guide" doesn't go into how to make one...I already had a pre-drilled one from another camera; I suggest having a look on YouTube for "how to make a pinhole"

I purchased a Polaroid CB-103 from EBay a couple of weeks ago. It cost $38 plus $10 shipping. Luckily, this one was in really good shape. In fact, it looked like it was unused. Prices for these things can vary widely. I try not to pay more than $50 after shipping, but I've seen them sell for as much as $100.

The CB-103 was designed for Polaroid peel-apart films, which isn't made anymore (most of the packs you find on EBay are not worth the money since there's zero guarantee the film will work). The good news is that this beauty processes Fujifilm brand instant films, like FP-100C, which are still made.

The first thing I did was determine the focal length I wanted. I decided on 50mm, which gives a pretty large angle of view (about 100 degrees). Next I measured the CB-103 from edge-to-edge. The short sides were 108mm, and the long sides were 150mm. Keep in mind that the foam core I used was 5mm think. Since I planned to keep the short pieces on the inside of the longer pieces, I subtracted 10mm (5mm*2). I measured and cut the pieces. This would allow me to create a box around the opening of the CB-103.

With the pieces held together with a little tape, I tried the box on for size. Deciding it looked good, i moved on to cutting the front of the camera.

Since the front piece would sit inside the other pieces, it measured about 140mmx98.

To make the area where the pinhole would go, I drew diagonal lines from corner-to-corner to locate the center. I then cut a hole about 5mm ...not quite square :)

I fit the top piece inside of the box to see how it fit. It doesn't need to be exact, in fact, expect there to be some gaps, like this one.

 The magic of gaffers tape is that it will cover any imperfections and block out light leaks. After cutting the center hole, I like to reinforce it with some tape.

I then tape the hell out of the outside of the box. I typically use about four layers of overlapping tape. Side note, gaffers tape is about 50mm wide, which fit the sides of this camera perfectly.

After I taped the box, I took it outside and sprayed a good layer of flat black tape to cover the white inside (cheaper and easier than taping it). This will keep light from reflecting and bouncing around inside the camera.

Let it dry. I played Gran Turismo 4 for about half an hour...yes, my PlayStation 2 is further proof that I'm an utter nerd (as if pinhole wasn't enough to clue you in).

After drying, I centered the pinhole (be sure to paint one side of it black if it's made out of reflective material) and taped it to the box. I then taped the box to the CB-103. The processing unit needs to open to load film, so have to be careful not to tape it closed. With mine, I cut away tape that went over the opening seam. I again used about about four layers of tape. The goal is to keep light from leaking through any gaps between the box and the CB-103.

Since I didn't know the exact measurement of the pinhole, I needed to test the camera to determine the f-stop. The great thing about using Fujifilm is that it develops very quickly, which means testing doesn't take very long (unlike a normal film camera, which requires waiting to develop the film).

I picked up film today at my local camera shop. It cost about $15, which is way too expensive. You can typically find FP-100C online for about $10. I should have waited, but I'm impatient.

The way I test is to pick a starting f-stop and meter for it. In this case, I started with f/144 and used a light meter app for my Ipod Touch. The first image was a tad dark, so I began metering for f/161, which was closer. After scanning, I believe it's actually closer to f/180. I also realize I don't like the pinhole, so will likely drill my own that's hopefully smaller and on a thinner piece of brass shim.

Here's the camera in action (a 10-minute shot in a mosquito-filled alley...the shot wasn't very good but at least the mosquitoes got to feast on me):

Here are a few of my test shots. Not keepers but they served the purpose of testing while providing a much needed walk and thinking time:

Good balance considering the large contrast between shade and light. Shot was about 15 seconds.

Just noticed there's something blocking the light from the film...perhaps some tape inside.

Too dark...reciprocity failure, perhaps since it was 10 minutes

If you have any questions about my process, of if I did a poor job explaining something, please leave a comment.