Introduction to Exposure

Written by Nanette

Sunday, 02 November 2008 00:00

Exposure is the amount of light allowed to fall on the photographic medium (the sensors in the case of a digital camera). This amount of light is a result of 3 combining factors.

ISO

The digital sensor's sensitivity to light.

Aperture

A moving diaphragm within the lens controlling the amount light passes through.

Shutter

An open and close device controlling how long the sensors are exposed to light.

Photographers sometimes mention the term f-stop when referring to a change in exposure settings. A 1 stop difference means doubling (or halving if negative) the amount of light of the exposure.

Changing the ISO from 200 to 400 is an example of increasing sensitivity by 1 stop.
Adjusting shutter speed from 1/125 to 1/250 is an example of a 1 stop difference.
Changing the aperture from f/8 to f/16, however, does not equal to a 1 stop change. But the change from f/8 to f/11 is a 1 stop change. This is due to the fact of how apertures are constructed and measured.

In the coming days I will write more details on the subject of exposure.