 Free Pinhole Camera Exposure Charts

To calculate the exposure time for pinhole camera, we first of all need to know the f number of the pinhole camera. Unlike normal cameras, this value does not change because the hole remains the same size which therefore simplifies the final calculation.

Pinhole  Number. This is the distance from the film divided by the diameter of the pinhole. Let’s assume that our pinhole camera has a focal length of 25 mm and the diameter of the pinhole is 0.18 mm . Using the information above, 25/0.18 = 138, so our working aperture f number would be 138.

Pinhole Exposure Calculation

The high numbers found on pinhole cameras in the majority of cases are not available on light meters. In order to get round this problem, we set the light meter to a different aperture, usually f 22, and then convert the measured exposure time for the aperture of the pinhole camera.

We do this by dividing the f number of the pinhole camera by the f number set on the light meter. We then square this number and use it to multiply the measured exposure time.

For example, if the light meter which is set to f/22 gives us a reading of 1/30 second, the calculation for our pinhole camera with an f number of  138 would be (138/22)2 = 39.3. The indicated time by the light meter has to be increased 39.3 times, resulting in an exposure time of  1.3 seconds.

Free Pinhole Exposure Charts & Exposure Guides

I have compiled a series of pinhole exposure charts for some popular pinhole f/numbers. The charts include pinhole exposure times for pinhole cameras with a different focal lengths and numbers.

(25mm f/138)  (40mm f/158)  (40mm f/235)  (50mm f/176)  (60mm f/207)  (75mm f/216)  