File last modified 4 January 1999
24.4 The Psychology and Physiology of Visualization
The way our eyes work and the way we think effect the perception we take away from any encounter with visualized data. This is important, how we present something can make a lasting impression, sometimes not always a good one. What we choose to emphasize and/or de-emphasize will be what the viewer does or does not take home. A bad choice in a color scheme can inadvertently draw the viewer's attention to trivial or inconsequential aspects of our analysis leaving them seriously under-impressed.
The first aspect of displaying our results should always be the contrast in the "image" we have prepared. Because of the way the human eye has evolved over the millennium we can really only perceive about 30 different shades of grey (Russ, 1999) at any one time. The receptors on the retina of the human eye are divided into two kinds: rods that perceive the level of light and cones that perceive color (Gonzales and Woods, 1992).
While we may be able to resolve about 30 shades of grey, our eyes are equipt with detectors sensitive to 100's of colors. These detectors (cones) are concentrated in and about the fovea (the point of focus of our eye upon the retina). Because we are so sensitive to small differences of color rather than small differences of brightness the use of false-color, or color lookup tables, has been a very popular means to help us distinguish small differences in intensities in imagery.
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