Illuminance

Illuminance
Is the term quantifying the illumination of, or incident light falling on a surface.

Illuminance is measured with a flat receptor. It is straightforward to compare an incident-light measurement using a flat receptor with a reflected-light measurement of a uniformly illuminated flat surface of constant reflectance. Using values of 12.

Illuminance - term quantifying the illumination of, or incident light falling on a surface.
Image - two dimensional representation of a real object, produced by focusing rays of light.

The illuminance (or intensity as it is sometimes called) is controlled by the aperture of the camera. The term illuminance means the amount of light reaching the film plane.

Here we use the term illuminance to specify only incident light. Both illuminance and luminance are typically measured in candelas per square meter (cd/m2). Approximate values for commonly encountered light sources are shown below.

This is one of those times when a very detailed mannequin, glass eyes, might have made a better subject.

See also: Exposure, Photograph, Luminance, Photography, Light