# Blender 3D: Noob to Pro/Understanding Real Lights

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In order to learn how to light a scene properly it is helpful to first
learn a few things about real lights. When you add a light to your scene
you need to understand how to go about emulating the properties of the
real light source that you want your Blender light to replicate.

## The Properties of Real Lights

### Color

Every light source always has a distinctive color of its own. A
photograph taken at sunrise or sunset is very easy to distinguish from
one that is taken at noon just by looking at the color of the light.
Incandescent light bulbs emit a light of a color that is different from
that of fluorescent light bulb. So a scene lit with one of the two will
have a different color cast when compared to the other.

### Angle

Light always streams in from a particular direction. The angle or
direction of light has a particular influence on which planes of an
object receive light and the shape and direction of the shadows that are
cast by objects receiving light from that particular source.

### Brightness and Decay

As light travels through space it decays or grows dimmer with distance.
Think of a firework bursting in the night sky. When the firework first
bursts the sparks are bunched close to each other. Over a short period
of time they quickly spread out from each other. If you replace sparks
with photons of light and the firework with your light source than you
have a very rough analogy to how and why light decays. All real lights
decay with distance according to the inverse-square law. At times when
lighting a Blender scene it becomes necessary to cheat this law.

### Shadows

Real lights will always cast a shadow of some sort. Real scenes also
typically include multiple sources of light (even if these are only
*indirect lighting* as a result of light bouncing off other objects).
Thus, even in an area shadowed by one light source, there will typically
be light coming from other directions, to soften the shadow so it is not
completely inky black.

### Size

Real light sources rarely take the form of tiny points; the light
usually comes from an area of discernible size. This manifests itself in
the form of a softness to the edge of the shadows, or
*penumbra*: areas behind an object where
the light is partially obscured are less dark than the inner parts of
the shadow where the light is completely blocked.

## 

These are not all the properties of real lights, but as far as CGI
lighting is concerned they are the most important. As we will see later
on, Blender offers enough controls for you to tweak and adjust each of
these key properties of light. 

