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Color Vision
Color Perception Factors

Environmental Factors

The color of the light used to view an image is probably the most important factor affecting its appearance. If you have ever compared a paint chip in a hardware store to the actual paint in the can versus the same paint on the wall, you know they can all look different. One of the biggest factors affecting these variations is differing light sources. Typical store light is a cool florescent, while home light is a warm incandescent and daylight streaming through an open window changes according to the time of day.

The brightness of the illumination affects the apparent purity of colors and the amount of detail visible in the shadows. In general the brighter the illumination, the more saturated colors will appear and the greater the amount of detail that may be seen in shadow areas.

Finally, the geometry of the illumination also affects the color and contrast of an image. Whether the illumination is coming from a small source or a large diffuse one, the angle at which the light strikes the image and the angle of viewing all affect the perceived appearance.

Circumstantial Factors

The surround is the area that appears in a person's field of vision when viewing color. The surround can be the background of the image or even the color of the walls and furniture in the viewing area. If the surround has a definite color(s), it affects visual evaluation in the following two ways:

  • First, any light that strikes the surround, such as brightly colored walls, is reflected onto the image and will change its apparent color.
  • Second, the eye tends to adapt to the color of the surround, so a colored surround will bias color judgement. Even brightly colored clothing worn by the viewer can sometimes have an adverse effect on the image being viewed.

Other light sources in the surround can also bias color judgements in much the same way. In defining white light we naturally associate it to normal daylight. But daylight changes constantly varying with the latitude, season, and time of day. Open north-facing sky contains more blue wavelengths while morning or evening sky is redder and has a correspondingly lower color reading.


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