Make an Adjustable Pinhole Camera

This instructable shows you how to convert a 60year old analog camera to a pinhole camera with three different pinholes.

First of all you need the camera. Tha agfa clack was introduced in 1954 and uses medium format film. But with a small modification you can also use 35mm.
I chose the agfa clack, because it is robust, cheap and easy to modify. You can get this camera for a few bucks in online auctions.
If the housing is o.k., don't worry about the function. There is nearly nothing that can get broken.

As a matter of fact, the hole is the most important thing for a pin-hole camera. But a hole would be nothing if there wasn't anything around the hole. :-)

This is a very thin sheet of aluminium. You can get that from a soda-can, a tea candle or something similar.

The key to a good performance of the pinhole camera is the hole.

The perfect hole is done in multiple steps. Do not just punch through, but make a small dent and polish it away. Dent to the other side and polish again. Do it as long as it takes to make a small hole.

Use this calculator for the best hole-size:
http://www.mrpinhole.com/holesize.php

I chose 0.3mm for the smalles hole, resulting in a aperture of 256.
I checked the size of the hole with a lead of a mechanical pencil, which is 0.3mm.

By the way: The makro-pictures were taken with my smartphone where I applied a laser-lens from an old CD-ROM-drive to the camera.

Now that you have one perfect hole make another one of different size.

I wanted to have aperture 64 and 16.
Therefore I needed one more pin-hole of 1.25mm and used the existing hole that was already there.
An aperture of 16 doesn't make sense if you want to remove the lens.

I also checked these with leads of mechanical pencils or other stuff I found around in the house. 1.25mm is aproximately the size of a rather thick pin.

Now disassemble the camera and glue the small sheets of aluminium with the holes to the existing aperture selector. 

Then I chose to black-out the back side to reduce reflections. Reflections can also be a nice feature, so try it without and if you don't like it, black-out afterwards.
You can use a candle to produce soot. But try it on some crap material first, because if you do it wrong you might destroy the aperture selector.

If you want a real pin-hole camera you surely have to take out the lens. But you can of course leave the lens in an gain some extra sharpness in the pictures. This is what I did, because I wanted maximum sharpness.

Now you only have to go outside an take a test on the new camera. I made myself a small sheet of paper to convert the reading from the light-meter for the new aperture of the pin-hole camera.
I have also taken account of the Schwarzschild-effect.
If you are working with very long exposures of some seconds and longer, the film doesn't react as calculated and you need to double the amount of time to give it the right exposure.
If you used the same appertures as I did, you can use the list below.
Take a lightmeter and measure at f8, then use the list to find the right exposure for your aperture:

f8	f16	f64	f64+	f256	f256+
1/500	1/125	1/8	-	2s	4s
1/250	1/60	1/4	-	4s	8s
1/125	1/30	2	1s	8s	15s
1/60	1/15	1s	2s	15s	30s
1/30	1/8	2s	4s	30s	90s

The columns with the "+" include the Schwarzschild-correcture.