What is photographic exposure? Exposure is the amount of light that falls onto the CCD sensor or film.


An over exposed image - too much light	A well exposed image - the right amount of light	An under exposed image - not enough light

To produce the desired density in the final image Photographic materials ( film, paper or CCDs) need to be exposed to a specific amount of light. Too much light and the receptor is over exposed - too little and it is underexposed -

In each of the extreme cases above (under or over exposure) visual information from the scene is lost.

So Exposure refers to the amount of light a light sensitive material like film, photographic paper or a CCD receives.

With the exposure of light sensitive materials, there are two variables ....

the intensity of light

or -the amount of light
that falls on the sensitive surface

and

the length of time the light falls on the sensitive surface or is exposed for

Three factors play a part in correct exposure:

• Aperture - the opening that lets light through the lens
• Shutter - The device that controls the length of time the light comes through the lens
• Sensitivity - ISO - or film speed - how sensitive the film is to light or the setting of the digital CCD sensor

While all of these interact with each other to produce the correct exposure, each one - Aperture, shutter and sensitivity has a different effect on the resulting image in other ways.

Comment on this resource

Want to learn more? - do a workshop or one on one with Lloyd Godman