Tutorial: working out aperture

So, you have your pinhole camera but it’s a matter of guessing the exposure times…

In analogue photography you work out the ISO of the film, shutter speed and aperture, right?

Use a ruler with half millimetre increments to measure the size of the pinhole. Then use the ruler to measure how long the focal length is from the hole to where the paper/film is loaded. Divide the pinhole size by the focal length.

For my Quality Street tin it was: 1mm/217mm= 217 (aperture)

If you are using photographic paper in the camera, it will have an ISO of around 4, which means that it is not as sensitive to light unlike film.

Use a light meter and set the ISO to 4 and measure the light. However, light meters only go up to apertures of 60 or 90 so you will have to work out how long it’ll be needed for.

Ap Shutter

1.4

1/2000

2

1/1000

2.8

1/500

4

1/250

5.6

1/125

8

1/60

11

1/30

16

1/15

22

1/8

32

1/4

45

1/2

64

1″

This table shows how every F/stop you go up, you need to double the time the shutter is open for.

F/stops after 64 go as follows:

90, 128, 180, 256

So, for example, at F64 I needed a 2 second exposure for outside; so going through the table, doubling the time, I rounded 217 to f256 to find that I needed 32 seconds.

Here are some photographs of my second pinhole camera made from a Quality Street (painting matt black inside to prevent light reflection).

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