Light that is absorbed by the subject is never again seen as visible light. The absorbed energy still exists, but the subject emits it in an invisible form, usually heat

Direct and Diffuse Transmission

the single most important quality of a light source is its brightness. A brighter light is almost always a better light.

We call the rate of fluctuation of the electromagnetic field its frequency, and we measure it with the unit called Hertz,

The subject can do three things to a photon

Light rays from a low-contrast source strike the subject from many different angles.

Materials such as white glass and thin paper scatter the light rays in many random, unpredictable directions as they pass through. This is called diffuse transmission

Transmission

One of these is 5500°K and is called daylight. There are two tungsten color temperature standards, 3200°K and 3400°K.