Pinhole design & exposure
Pick a focal length (film-to-pinhole distance) and get the sharpest pinhole size, its f-number, and a metered exposure scaled to it.
Optimal diameter uses d = 1.9·√(f·λ), λ = 0.00055mm. Long exposures also need reciprocity correction — add more time for your film.
About this tool
A pinhole camera has no lens, so its sharpness and brightness depend entirely on the hole size and its distance from the film. Enter the focal length and a metered f/16 exposure, and this tool returns the optimal pinhole diameter, the effective f-number and the exposure time before reciprocity. It helps you build and shoot a pinhole camera with confidence.
How to use it
- Enter the focal length, the distance from the pinhole to the film.
- Enter your metered exposure time at f/16.
- Read the optimal pinhole diameter, the effective f-number and the base exposure time.
FAQ
Why is there an optimal pinhole diameter?
Too small a hole blurs the image through diffraction, while too large a hole blurs it geometrically. The optimal diameter, which grows with focal length, balances the two for the sharpest result.
Why does the tool mention reciprocity?
Pinhole f-numbers are very high, so exposures run long. At those durations film loses sensitivity through reciprocity failure, so you must add extra time on top of the calculated base exposure.