Ever felt your SLR takes too high quality images? Long for the simpler days? Here is a very simple way to make a high quality, easy to use pinhole to replace your SLR lens.
Step 1: The Raw Materials
You need just three things for this pinhole "lens":
1. A body cap for your camera (I got a spare one for £1 on ebay)
2. Some thin metal (eg. foil, the side of a drinks can)
The trick of this method is using the body cap as the support for the pinhole. It is a perfect fit for the camera, has no light leaks, is easy to fit and remove (with no chance of causing damage to the camera) and is easy to modify. The thin metal will be used to make the actual pinhole, any piece of thin and soft metal (aluminium is ideal) will do.
Step 2: Drilling the Body Cap
Drill a small hole (~5mm) in the centre of the body cap. The plastic is normally soft and any wood drill bit will have no problems. Make sure the hole is dead central; measure and mark before you drill! The hole only needs to be small, a pinhole has a very small field of view and a 5mm hole will not obstruct the edges of the view at all. Make sure you clean all the dust off from drilling!
If you don't have a drill a penknife (or similar) will work just as well, but will take more time. Make sure you don't damage the cap otherwise you will get a light leak.
Step 3: Prepare the Pinhole
The best way to make the pinhole will depend on which material you are using. For something very thin (like foil) a simple pinprick will probably work. For thicker materials thinning the metal with a penknife then making the actual hole with a pin works well. You want to aim for a pinhole of around 0.2 to 0.5mm, the larger the pinhole the brighter, but more blurred, the image is. There is no point going smaller than 0.2mm because then diffraction effects start blurring the image.
Make sure you use a circular pin, and twist it slightly as you push it through the metal. The more circular a hole is the better image it gives. If there are any small flakes of metal around the hole trim them off with a knife as they can also disrupt the image.
Step 4: Assemble the Pinhole and Body Cap
When you are happy with a pinhole simply tape it over the back of the hole in the body cap (make sure you line it up!). Try to tape the pinhole nice and flat over the back of the body cap to reduce light leaks. You can use black tape (eg. insulating tape) or black marker pen to block light getting around the edges of the pinhole if you think you might get light leaking problems.
Step 5: Testing the Pinhole
The easiest way to test the pinhole to put it on your camera and try a few shots, but you can also test the pinhole with a laser pointer and looking at the diffraction pattern. The diffraction pattern is very sensitive to the shape of the pinhole and makes it simple to spot if the pinhole shape is a problem.
All you need to do is shine a laser pointer through the pinhole onto a flat surface (a wall or piece of paper) a couple of metres away. Green lasers work best (because they tend to be brighter) but you can also use a red laser. A perfectly circular pinhole will give a diffraction pattern of a series of rings around a central bright spot. A typical good-quality handmade pinhole will give three, or even four, unbroken rings around the central bright spot. If you only get one or no rings then it is definately worth remaking the pinhole.
Step 6: Taking Pictures
Taking pictures with a pinhole camera isn't easy or particularly spectacular, but it is fun! The pictures will always be blurred and will need a long exposure (try around 2sec for a brightly lit room, 0.5 sec for outside) but do give a wonderful diffuse glow and dreamlike appearance.
See below for a couple of indoor examples (no outdoor pics sadly, the weather is terrible!).