Pinhole photography is basically nothing more than taking a photograph through a hole the size of a pin. It has been around as long as photography has been around, and for 2000 years or so before that painters used a similar technique in order, for example, to paint murals. They used a dark room with a tiny hole on one side that projected the outside scene on the opposite wall. Sounds familiar? Good! I have just described a Camera Obscura. Pinhole photography is basically the same thing. Pinhole lenses are relatively easy to make, you take a piece of aluminium foil, punch a tiny, pin-sized hole in it, and mount it on the camera instead of a lens, making sure that the hole is as round as possible and centered in front of the sensor. Alternatively, you can buy a pinhole lens for your camera. That’s what I did.
There are formulas to calculate the ideal diameter of the pinhole. (there is even an app for that) which varies according to the focal length or, in this case, the distance from the foil to the sensor. As a rule of thumb, the shorter the distance, the smaller the ideal hole. For a 50mm equivalent for instance, the hole size should be between 0.25 mm and 0.30 mm. That tiny hole functions as an aperture on a normal lens, but much smaller. We deal with apertures in the f195 – f200 range here instead of the normal range of f2.8 to f16 or there about for a 50mm lens. Now, in photography, the smaller the aperture, the larger the part of the image that is in focus, so one would think that with an aperture of f195, everything would be in focus and, technically speaking, it is. However, there is a snake in the grass, and that is diffraction. Nothing in the image is sharp. Even though you can see detail, it is always a little fuzzy. Without getting too technical here, that fuzziness is because light rays have the ability to bend around flat surfaces, but by doing so, the light rays become slightly distorted and are not exactly aligned anymore. This is called diffraction and causes the image to look a little fuzzy. The same phenomena occurs also with normal lenses and becomes generally noticeable with apertures smaller than f16 or so, depending on the lens. Using a larger or smaller hole size than the ideal hole size will also influence the sharpness in a negative way.
The other thing is that the camera does not communicate with the lens. There is nothing to communicate with: it’s a hole in foil! No adjustments, no electronics, no light meter. Nothing. The only technical thing you need to do is to set your camera on manual and, once you are ready to go, calculate the shutter speed based on the Sunny f16 rule (or with a separate light meter).
For those who don’t know what the Sunny f16 rule is, this assumes that on a sunny day, the aperture will be f16 and the corresponding shutter speed will be the closest setting to the ISO being used. So, if you use ISO 100, the shutter speed will be 1/125 sec., based on full stops. If there is cloud covering and the subject is in the shade, but still very bright, the aperture will be f11 with a shutter speed of 1/125 sec., severe overcast will be f8 with 1/125 sec., and so on.
Since a pinhole has a fixed diameter, it is not the aperture that changes, only the shutter speed. The ISO setting can be left at 100 ISO. Of course, the thing is that you are not using f16 or any of the “normal” apertures, but f195 or so. This means that whatever shutter speed you came up with needs to be recalculated to the shutter speed corresponding to f195. Because of this awfully small aperture, your 1/125 sec. shutter speed can easily turn into 3, 4, 5 seconds exposure or longer. Fear not though, there are smart phone apps that can help you with those calculations.
Keep in mind that because of the tiny hole size, the viewfinder will be dark and so will the life view. (if your camera has that option). There are two ways to solve this problem; there are manufactured pinhole lenses available with the different hole sizes built in. With these lenses, you can use a larger hole size to compose and then readjust the lens to the ideal hole size or the size of your choice. The other option is to compose with a regular lens and then switch to the pinhole lens to make the exposure.
So, why in the world go through all this trouble for a fuzzy picture, you ask? But what a fuzzy picture it will be! It could be an acquired taste, but there is something special about a pinhole photograph, and pinhole photography is great fun. It is old school, sure, but this step back in time makes you realize what photography is all about: light, composition, and your imagination.