I started to read “Light, Science & Magic”
A few notes:
Light is energy. Variations in the energy is seen by the human eye as colour. At least the parts we can see.
How to describe light?
Brightness: if things are not bright enough we cannot photograph them. We control it through aperture, speed & ISO.
Colour: our eyes and mind see white light if there is a reasonable balance of the primary colours. The colour temperature scale was pinched from science. Things considered hot on this scale are seen as cool i.e. blues. Warm colours have low kelvin scores. Imagine a burning match and a welding torch. 5500k is daylight.
Contrast: a light source has high contrast if its rays all strike from the same angle. Low contrast light sources come from many angles. Sunlight is high contrast no light enters the shadow areA. Shadows are sharp and defined. In cloud light is scattered and comes at the subject from many angles. We can see the type of light source by its shadow. In low contrast light the shadow is no longer clear. The edge is not defined. When we talk about hard and soft shadow it relates the edges. The shadow can still be light or dark. Small light sources are hard light sources. Larger = softer. Other things can change these rules. Lighting attachments/distance etc.
Exposure can effect contrast. Increased exposure of dark subjects may increase contrast.
Shadow is where light does not strike.
Highlight is the area illuminated.