Saturday, May 15, 2010

Local versus Perceived Color

Local Color

Local color refers to the actual, physical color of a surface independent from the effects of light and shadow.  Local color is the answer you give when someone asks you "What color is it?".  For example, if you had to fix a hole in a wall, you spackle up the hole and then paint over the repaired area with paint that matches the local color of the wall. If I asked you what color your shirt is, you would respond with its local color.  This color wouldn't change regardless of the lighting situation- even in the dark you would still say the same color.

Perceived Colors

Though it is almost always extremely helpful to know the local color of an object you are painting, often you will not actually mix the local color and use it in your painting.  This is because the effects of light and shadow create many variations of this local color, which we will call Perceived Colors.  This is what actually reaches your eye in the form of rays of light- not the local color.  However, the human brain seems to be geared towards processing the perceived colors and determining the local color of an object.  If you see a green apple, you understand it as a green apple, not a dark green, medium green, and light green apple.  Most children begin coloring by using the local color to fill the entire area of an object.  It's only later that we become aware of "shading".

Perceived colors includes the shading created by light, along with other effects such as the color of the light, the texture and material of the object, it's position relative to the light, and many more.  Perceived colors can vary greatly with a change in any of these factors.  Note that colored lighting especially can dramatically alter the perceived color.

A computer graphics scene of colored objects.

The local colors of the objects in the box,
ignoring light & shadow

The perceived colors under white light, yellowish light,
bluish light, and very red light (clockwise from top left).

In the examples above, notice that the local colors of the objects rarely, if ever, appear in any of the lit scenes- particularly when the light source is colored.

What Does This Mean For the Painter?

If we want to paint realistically, we need to paint colors that mimic the perceived colors.  If we put them down skillfully, they will cause the viewer to understand the objects in our painting appear to have the same local colors as the objects did in real life.

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