Hands on: Make a digital pinhole camera

So the optimal-sized hole for a dSLR with a focal length of 50mm has a radius of 0.165mm – a diameter of approximately a third of a millimetre.

There are a number of other formulas but this one appears to be the most popular, probably because of its simplicity.

You’ll find some of the others on the sites detailed in the web links below, some of which have Javascript calculators.

Having determined the maximum optimal aperture, the obvious question is how do you make a hole one-third of a millimetre in diameter?

I inserted the smallest needle I could find straight into the foil to a sufficient depth so that the widest part of its shaft was buried.

Then I scanned the body cap pinhole assembly on a flatbed scanner at 1,200dpi, which, when viewed at actual pixel size, allowed easy measurement of the hole diameter – 0.6mm.

I made a second attempt using the same needle (it was the smallest one I had), but only inserting the tip. A second scan revealed this hole to be 0.36mm in diameter, though not exactly circular. Good enough, I reckoned.

Aperture and exposure
To calculate the effective aperture for your pinhole camera, you can use the formula f = v/d where f is the aperture, v is the focal length and d is the pinhole diameter.

For my modified pinhole EOS 300D this is 50/.33 = f152. This minuscule aperture is what gives pinhole photography one of its defining characteristics, virtually unlimited depth of field. Everything from the close foreground to infinity is in focus.

It does have one practical disadvantage though – it requires exposure times ranging from several seconds to a few minutes. Clearly there are some subjects for which pinhole photography is not well suited, but for landscape photography and even portraiture, excellent results can be achieved.

Using the camera
Obviously, with exposures measured in seconds, you’re going to need to mount the camera on a tripod or some other steady surface.

The low levels of light transmitted through the pinhole render the viewfinder virtually useless, so you just have to point the camera in the general direction of the subject and hope for the best. You can always adjust it if your first attempt isn’t accurately framed.

You’ll also need to experiment with exposures to find the right shutter speed. As a general guide, start by shooting outside on a bright day with an ISO setting of 100 and make an exposure of about 10 seconds.

You can go from there depending on how the thumbnail looks. I’m pleased with my first pinhole image, despite the fact that it’s poorly framed, overexposed and, because my pinhole wasn’t centrally located, vignetted on the top-left corner. One of the advantages of using removable foil pinholes is that you can adjust them like this to get them positioned in exactly the right place.

With the pinhole relocated and some exposure tests, I produced an image of a willow tree in my garden, with an exposure of two seconds at ISO 800. The Exif data for these pinhole images makes interesting reading.

In the absence of a proper lens, the focal length is shown as 0, the exposure details indicate two seconds at f0 and the maximum aperture value is f1,024. Other than that, all the other Exif data is recorded normally.

I conducted further experiments indoors. An image of some roses was made under halogen room lighting at 800 ISO, with an exposure of 20 seconds. As you’d expect, it shows the characteristic softness of pinhole photos. It’s also pretty noisy and there’s some sensor dust that’s a lot more visible than it would be with the lens attached.

I haven’t tried to improve my images using an image-editing program as this runs contrary to the whole ethos of pinhole photography. My digital pinhole experimentation has been great fun. It has even inspired me to make a genuine pinhole camera using discarded food packaging and a packet of Ilford photographic paper that’s been sitting in a draw for about 15 years.

Web links:
Worldwide Pinhole Photography Day Upload your pinhole photos taken on 27 April 2008 and see images from previous years.

Pinhole photography forums

Some good advice, pictures of the pinhole cameras he has designed and a Windows applet called Pinhole Designer, which helps with pinhole size, focal length and exposure calculations

Article and advice on the physics of pinhole photography

A history of pinhole photography and advice on building a camera

Pinhole cameras and kits on sale