Exposure Reciprocity in Photography

Por FreeJpg Editor

Posted on 2016-07-15

In today's article we elaborate on "The law of reciprocity". When we refer to photograph reciprocity in its technical definition it is; the opposite relationship between the intensity and duration of light that provides the reaction of a light sensitive material.

But now put a slightly less complex example.

Imagine that we need to fill a glass with water, depending on the amount of water to be pouring into the glass is filled in less or more time, but will always meet in order to fill the glass. The same happens if we need to fill light sensor our camera.

Suppose a correctly exposed photograph, is a full glass of water, controlling the amount of light let into the diaphragm, we will get by opening or closing the same. The more we open the aperture, the more light to enter, and the less time we will need. His technical definition can be confusing, but with a simple example all doubts are dispelled.

If we have to photograph a certain subject and the camera to measure exposure indicates 1/60 of speed and f / 16 aperture. Assuming you are doing portrait photography, this openness is not the most appropriate. If to use an aperture of f / 2, while maintaining the correct exposure to calculate the camera, this is where comes into play the rule of reciprocity. This rule, being inversely proportional indicates that we will get the same exposure using these values:

In the following video tutorial, it will be explained simply any doubts generated by this law.