• Pinhole Blender Exposure Calculator •

Use this calculator to convert exposure data from any light meter to the pinhole size of your Blender. Set the ISO for the film in your blender on your meter. Take a reading from your subject. Read across the f stop to the displayed shutter speed. The corrected shutter speed for your blender will be listed directly below. All Pinhole Blenders come equipped with an f 200 pinhole aperture. The Pinhole Blender mini 35 and mini 120 also come with a f 64 zone plate.

About Reciprocity Failure

Exposure is given by a pair of parameter, they are: Time and Aperture, there is a reciprocal relationship between them. That means that if you increase one of the values by a factor and decrease the other by the same factor, the exposure will be the same. An example: 20 times 40 is equal to 800, but if you halve 20 and double 40, their product will also give you the same result 10 times 80 equal 800. Another example: f/60 @ 1/200 sec's = f/90 @ 1/100 sec's.

Unfortunately, when your exposure time gets below 1 sec or higher than 1/1000 sec, that reciprocity between Time and Aperture fails, hence Reciprocity Failure. The effect is that you will need to expose for longer than what the reciprocal relationship is telling you. Each film has its own characteristics, therefore, each film FAILS in a different way.

Exposure times over 1 second in the above chart has been corrected for reciprocity using a general formula. Since each film stock has its own properties it is best to check the manufacture guidelines for the most accurate corrections.

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Contents copyright © 2007 by Chris Peregoy