Three characteristics of Light
1) Brightness, often times called intensity in your 3D package.
2) Color, usually described as color temperature, as borrowed from physics class.
When you heat a material in a vacuum, burning hot, it will glow. The color of this glow depends on how much heat is applied. The measureing unit of this heat is in degrees Kelvin. As a twist to the artist sayings of warm up the image by adding more red, the hottest flame coming from a blow torch will be blue - white. So that means 10,000K light is much more blue, and a lower heat 2000k light is more red and yellow. Photographers use three standard light color temps, one of which is 5500k called daylight. Then there are two common tungsten color temperature standards, 3200k and 3400k, where you can buy film that is color balanced for these temps. Digital cameras have more flexibility and can shoot color balanced photos at ranges higher and lower then these three commonly used. Then with your 3D application any Kelvin number can be put in allowing for a huge range of color variety.
3) Contrast
High contrast light - when all rays from this light strike the subject at nearly the same angle.
This light will have sharp shadow edges, produced by small light source, the sun, in CG a point light or a directional light. Will cause a sharp highlight when hitting a surface, but this can depend on the material.
Low contrast light - when all rays from this light strike the subject from many different angles.
This light will cast soft shadows, produced by a large sized light source, like overcast sky illuminated by the sun, big box lights, soft box, light tent, and in CG a scaled up area light, or full white sky dome. Will most likely cause a large spread out softer highlight, but again this is also related to the material properties.
Three characteristics of Subject
Or three characteristics of the Material.
When light hits an object it will either be transmitted, absorbed, or reflected, that's it.
1) Transmission
