Thursday, March 6, 2008

matchbox pinhole

My first couple of 35mm pinhole cameras attempted to be panoramic, wide angle affairs, but this time I thought it would be nice to get back to the classic square format.
Here's my latest contraption which uses 35mm film to provide square images of 24 x 24mm. Using this size means that you can get up to 50 exposures on a standard roll of 36 exposure film. Now that's what I call economy!
The image edges suffer from distortion that gives a "Diana" quality to the pictures. In fact, the images look very "toy camera" like indeed, except that the pinhole allows some really good close ups due to the DOF of the pinhole.
It's also costs pretty much nothing to build - certainly a lot cheaper than a $100 Diana off ebay!
So far I've only run a single roll of colour film through it, which I then developed in B&W chemicals,so the results are a bit odd but they did prove it worked.
I'll be posting additional photos (colour too!) onto my flickr site, check it out.

All you need is a matchbox, an empty roll of 35mm film, some new 35mm film, some black tape and a bit of foil!
First, mark out a 24mm square exactly in the centre of the matchbox tray, cut this out with a sharp knife as neatly as possible. Or make it messy if you like, it's up to you. This provides the image frame, any rough edges or card fibres will appear on the image obviously.

Now get a black pen and color the tray black. Also stick a pen inside the front of the sleeve and colour that black too.

Cut a small hole, about 6mm square, in the centre of the sleeve. Try to do this as neatly as possible to avoid fluffy fibres appearing in the image

Now for the pinhole. The very short focal length means that the optimum pinhole size is small, less than 0.2mm. Make a pinhole in a bit of foil/drinks can using you favourite method (wont go into it here, search the web), and stick it over the hole in the sleeve.

To work out how far to wind the film, I make small "clickers" from bits of plastic (here that stuff used to bind documents). Cut a very thin strip and make a point at one end

Now take the full roll of film. Stick the curved plastic to the back of the canister so that the pointed end pokes through a sproket hole by about 3mm. As the film is pulled out of the cansiter, the plastic will jump between holes and make a clicking sound. (some more detail on this here)

Now thread the film through the box sleeve. Then, push the inner tray in so that the base of the tray with the hole in in presses against the film, pushing it flat and proving the square frame.

You also need an empty spool to take up the film. Ideally, this will still have a bit of film sticking out, otherwise you have to carefully open the canister with a bottle opener, fix the new film end to the spool and re-assemble. I've done this but its much easier to use a spool with some film sticking out!! Splice the film together with clear tape. Then, wind the film into the take up canister so that both canisters fit snugly against the matchbox. Make sure no film is visible at the back - you will use tape to seal this joint so you dont want to be sticking tape onto the film! NOTE - make sure you dont wind the film back into the full spool at any point, the "clicker" plastic may rip the film.

All that remains is to make the thing light-tight. Wrap tape around the joints between both canisters and the box. Make sure all sides are well covered. The tape does a suprisingly good job at keeping the whole thing together and stable!
Place a small piece of foam on the underside of the takeup canister then wrap tape over it. This gives some tension and stops the film unwinding withing the canister each time you wind on.

Now make a simple shutter, a bit of tape will work, but I prefer a sliding card shutter. The camera's now ready to take pictures! Find something suitable to wedge into the top of the empty spool to act as a handle to wind the film on, and count 6 clicks for each frame.
Check out to calculate the optimum pinhole size, and work out exposure times for the film you use.
Mine worked out at around f90, which gives fairly short exposure times with ISO100 film, a second or two in daylight.
Make sure you don't wind the film back into the canister with the plastic "clicker" attached - it will rip the film.
Here's some more images from my first test - note I didnt get the hole exactly square!
If you decide to make one of these please share your images, I would love to see them. If you are a flickr user I've created a group called Matchbox Pinhole - Please add your photos to the pool! :-)


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