DSLR camera and spare body cap
Drill and 1/4 inch (or larger) drill bit
Aluminum foil
Scissors
Black permanent marker
Electrical tape
Small pin
Magnifying glass or loupe (the more powerful the better)
Ruler with millimeter markings

Making the pinhole:

Cut a few pieces of aluminum foil about 5X5cm (2X2 inches) in size.
Use a black permanent marker to blacken the dull side of one of the pieces of foil.
Place the blackened piece of foil between a couple other pieces of aluminum foil.
Place the stack of aluminum foil strips on a piece of wood.
Take a small needle and gently pierce the aluminum foil stack (rotate the needle as you push).
You don’t need to push all the way through the stack of foil, just push deep enough to get the size hole you want in the blackened piece of foil. This will take some trial and error.
Remove the blackened piece of aluminum foil and inspect the pinhole with a magnifier.
Make the pinhole as round and as smooth as you can, this will help produce the best quality image.
Repeat this process until you have a pinhole the diameter you want (use the calculator below).

After you have a pinhole you like, trim it and tape it to the body cap with the blackened side pointing toward the sensor. Try to place the pinhole in the center of the hole in the body cap. You can drill the body cap hole larger if you find this size causes some vignetting in your image (if you are using a camera with a larger digital sensor).

For your first attempt, don’t worry too much about getting the exact size pinhole but try to get one that is round, smooth and as close to the size you want.

Recording images with the pinhole camera:

Place your camera on a tripod or stable surface.
Set your camera on Manual Exposure mode.
Set your ISO to 100 (this can be changed to any setting you like later).
Set the camera so you can see the histogram when you review the image you just recorded.
Turn on "Live View" if your camera has this feature, you might be able to see an image on the screen which will help you compose your images.
Set the camera’s self timer to delay a few seconds after the shutter is tripped. This will help lessen vibrations.
Record an image with a 2 second exposure (on a bright sunny day).
Review the images and adjust the shutter speed according to the histogram information.
Repeat this process until you are happy with your exposure.
You are now recording digital pinhole images. Have fun!

I used a Canon 90D camera which has an APS-C (22.3 x 14.9mm) sensor. Because this camera has such a small sensor, I was interested to see what kind of image I would be able to create. I measured the distance from the sensor to the pinhole to be 52mm which meant I needed a pinhole with a diameter of 0.26mm (F# 200). This combination of pinhole to sensor distance, and the camera’s small APS-C sensor, created a horizontal field of view of about 24 degrees which is about the same as an 83mm lens on a full frame (35mm equivalent) camera.

Images recorded with DIY digital pinhole cameras tend not to be as sharp as those recorded with larger format film or photographic paper cameras (not that any pinhole images are really that sharp to begin with, that's the beauty of this style of photography) but they are much easier to create and do not require film processing or a special darkroom setup.

Worldwide Pinhole Photography Day is the last Sunday in April so give this a try and have fun creating your own unique pinhole images.