let's make a pinhole polaroid camera!
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Finding location...
Duchamp
says:
A few weeks ago I attended a pinhole camera workshop by Dave Kemp at InterAccess. This workshop was a real inspiration, and since then, I've been going a little bananas with this whole pinhole thing. It's also helped me understand a bit more about regular photography.
I thought I'd pass along some of what I learned.
In the workshop we used photographic paper as a negative in our pinhole cameras, and we had a darkroom setup with all the developing chemicals and timer, etc. I'm a little too impatient and lazy to mess around with that stuff, so I've been toying with using sheets of Polaroid 600 film to get instant gratification.
For this pinhole camera, we'll use aluminum foil baking pans. I found a pack of 5 tins for about $1.50 in my local grocery store. These tins come with cardboard lids.
Paint the inside of the tin black, to stop light from bouncing around. If you don't do this, the final image will look foggy.
This is the hardest part of the whole process of making the camera. Living in a condo, I don't really have a work space to spray paint stuff, so I had to do it with everything inside a plastic bag. Not fun. I had to do about 3 coats to cover all the shiny spots.
Measure the depth of the tin, up to the inner rim where the lid will rest. (I used calipers, but a ruler will do) This will be the distance from the pinhole to the film, or the focal length.
Measure the diameter of your pin. This will be the size of the hole, or aperture. I'm using a fairly regular sized pin which is about 0.6 mm.
Carefully poke a hole right through the tin.
There ya go. A pinhole.
The F-stop of this camera is calculated by dividing the focal length by the aperture.
In this case... 35mm / 0.6mm = 55
So this is an f 55 camera. You can round up to f 60 if you like. Using the pinhole exposure calculator at mrpinhole.com, you can make a chart to convert from another f stop to another.
More on exposure time later...
(DO THIS STEP IN COMPLETE DARKNESS)
In total darkness, slide a sheet of Polaroid film out of a Polaroid cartridge.
With a little bit of tape, fasten the film to the inside of the cardboard lid. You'll want to put the film in upside down. (I mark the outside of the lid with an arrow pointing up)
(DO THIS STEP IN COMPLETE DARKNESS)
Place your the lid with film into the tin, and crimp the edges closed.
(DO THIS STEP IN COMPLETE DARKNESS)
Place a double layer of tape over the pinhole. Curl a little flap over so you can easily peel it off. This is your shutter. To take a shot, you'll peel this off and expose the hole, and then put the tape back on.
(DO THIS STEP IN COMPLETE DARKNESS)
You'll probably want to tape up the seams to stop light leaks. It's not entirely necessary, since the leaks can look pretty nifty.
There ya go. A complete polaroid pinhole camera.
Here's the business end of the camera.
There's no need to ever focus this camera. Since there is no lens, there is no need to focus. Things in the foreground will be in the same amount of focus as things in the background. It's infinite depth of field. I never really understood this concept until I started to fiddling with pinhole. A lens bends a point of light like a cone, and when in focus, the tip of the cone hits the film. When stuff is out of focus, the tip of the cone is not quite at the same distance as the film. This isn't the case with pinhole. With pinhole photography, instead of a cone of light bent by a lens, it's more like straight shafts of light from the subject to the film. The size of the pinhole determines the sharpness of the image.
Metering
If you have a light meter, then lucky you, but for the rest of us, we'll use our other "real" camera to meter. I set my camera to the same ISO as the Polaroid 600 film, which is ISO 640. I then set the camera to aperture priority and set the aperture to f16. With a half-press the shutter release on the camera to meter the scene, we get the exposure time at f 16 at ISO 640, in this case a 2 second exposure.
Now using the chart generated at mrpinhole.com, we see that the equivalent exposure time for f55 is 24 seconds.
That's a pretty long exposure time, so this is where things get a little tricky with Polaroid film. The film isn't designed to be exposed that long. There is a this thing call "reciprocity law failure" to account for. Basically, after about a couple seconds, the film's ability to capture an image is reduced, so to compensate, we're going to take that calculated exposure time, and multiply it by some number.
It took a lot of mucking around in a spreadsheet, but I've figured out a chart for compensating for the exposure time.
calculated exposure time --> Polaroid 600 exposure time
1/30 Secs --> 1/30 Secs
1/15 Secs --> 1/15 Secs
1/8 Secs --> 1/8 Secs
1/4 Secs --> 1/4 Secs
1/2 Secs --> 1/2 Secs
1 Sec --> 1 Sec
3 Secs --> 4 Secs
6 Secs --> 8 Secs
11 Secs --> 16 Secs
22 Secs --> 33 Secs
45 Secs --> 1 Min 13 Secs
1 Mins 29 Secs --> 3 Mins
3 Mins 59 Secs --> 9 Mins
6 Mins 58 Secs --> 18 Mins
12 Mins 57 Secs --> 44 Mins
24 Mins 54 Secs --> 1 Hour 4 Mins
48 Mins 49 Secs --> 3 Hours 40 Mins
So, for my test shot that metered for 2 seconds at f16 converts to 24 seconds at f55 but instead we'll expose it for about 40 seconds to account for the reciprocity failure of the film.
Once you have taken your shot and put the tape back over the pinhole, you'll need to process the shot.
(DO THIS STEP IN COMPLETE DARKNESS)
Integrated Polaroid film is developed by squishing the gooey chemicals in the thick part of the white border over the exposed film surface. You could use some sort of really hard roller like an acrylic brayer on a hard surface, which would be really DIY, but I opt for an easier and more reliable way to roll the film.
(DO THIS STEP IN COMPLETE DARKNESS)
I use rollers from a broken Polaroid camera. This is the "jaw" part of the camera that covers the film compartment.
Place the fat part of the film sheet into the rollers and crank the gear to run it through.
Tada!
There ya go. This would look a little sharper if I could sit still for 40 seconds. Since we're not using a negative, and the image isn't being made using a mirror like inside a regular Polaroid camera, the final image is flipped backwards horizontally. I think that's just kinda one of cool things about this kind of pinhole polaroid photography. You'll find that the shots are a bit disorienting, like some sort of snapshots of a parallel mirror world.
Posted 24 months ago. ( permalink )