Pinhole Exposure

Pinhole Exposure Calculation

Pinhole photography is becoming more and more popular for different reasons. For some it’s a way of starting out in film photography and for others, it’s a way of exploring different techniques, going back to bare basics and homing in on their skill levels.

I personally use a ZeroImage 2000 camera which uses 120 roll film and produces 6×6 medium format negatives.

A friend of mine, Martin Henson uses a ZeroImage 54 which is a 5×4 pinhole camera which produces 5×4 negatives.

Pinhole cameras have a very high aperture f number due to the size of the pinhole used. In most cases, these high aperture values exceed what a traditional light-meter can use.

Calculating Pinhole Exposure Times

Fortunately there is a simple workaround which we can use which allows us to measure the light with our light-meters at a given f number and then work out the correct exposure for the pinhole camera.

Let’s look at an example at calculating pinhole exposure time by using f/22 on our light meter.

Pinhole Exposure Multiplier

If we divide the f number of our pinhole camera by f/22 ^2 this will give us an exposure multiplier number.

Zero Image 2000 f/138

Dividing the 138 by 22 ^2 gives us 39 so in the case of the Zero Image 2000, the multiplier is 39. If we place a sticker on the camera with M39 on it, when out in the field, all we do is take the exposure reading at f/22 and  x it by 39.

One thing to remember is that this time does not take into account any film reciprocity it may have.

Our light-meter set to f/22 says the exposure time is 1/4 of a second. Multiply 1/4 x 39 = 9.7 seconds.

Zero Image Exposure Charts

To make life easier, I created a set of exposure charts for both the Zero Image 2000 and Zero Image 5×4 pinhole camera. The 5×4 Zero Image can accommodate up to three focal lengths, 25mm, 50mm and 75mm. The exposure charts include all three.

Zero Image Exposure Charts


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