How do you estimate the aperture (f-number) of a DIY pinhole camera?
Asked 4/27/2013
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I’m making a simple pinhole camera using a small hole made with a drawing pin or needle in thin aluminum (for example, cut from a can or foil). How can I calculate the effective aperture (f-number) of the pinhole, and what range is typical for a matchbox or DIY pinhole setup?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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If the diameter of the shaft of a standard pin is about 0.5 mm, then the aperture of that is based on the focal length and that should be the distance between the sensor and the lens mount (flange focal distance). So, given that, the math is: FFD/2 assuming a 0.5 mm pinhole. So, on a Canon EF mount with a 44mm flange focal distance, the aperture is f/88.
For formula purposes:
aperture = flange focal distance/diameter of pin
Originally by user472. Source · Licensed CC BY-SA 4.0
user472
13y ago
0
Generated from our catalog & community — verify before relying on it.
For a pinhole camera, the effective aperture is calculated the same way as an f-number:
f-number = distance from pinhole to film/sensor ÷ pinhole diameter
So if your pinhole is about 0.5 mm across and the distance to the film/sensor is 44 mm, the aperture is about 44 ÷ 0.5 = f/88.
That means the key measurements are:
- pinhole diameter
- pinhole-to-film/sensor distance
A very small needle-made hole in thin aluminum often ends up roughly in the f/95 to f/120 range in practical DIY use, though it depends on the actual hole size and camera depth.
If you want more precision, measure the hole diameter directly, or use an optical method such as shining a laser through the pinhole and estimating the diameter from the diffraction pattern. But for most DIY pinhole cameras, using the formula above with a reasonable estimate of the hole size is enough to get close.
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