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Summary:
Surface reflections affect the appearance of images in a variety of ways, depending on viewing conditions and the types of media used. Light projected to the eye from surface reflections does not carry information about the image; therefore, the reflection can be regarded as noise which interferes with the interpretation of the image. Light projected to the eye from surface reflections does not carry information about the image; therefore, the reflection can be regarded as noise which interferes with the interpretation of the image. Different media are characterized in part by surface reflection properties. Ink on paper, for example, provides a complete range of surface properties from glossy to mat. Since it must be viewed by reflected light, as it becomes less glossy there is a desirable decrease in sensitivity to viewing angle at the cost of a loss of image contrast. A CRT surface is rarely flat and never completely mat; therefore, it will allow directional reflections to interfere with the viewed image. Internal reflections and light reflected fro the surround will also produce noise. Such surface properties combine with other factors to affect significantly the appearance of images. To enable the images to be directly compared, conditions affecting visible surface properties must be controlled. Some simple models of surface interaction with light are presented here to help in understanding their causes, their effects on the image, and how to control them. Viewing of images involves several elements and an infinite set of conditions. Three elements necessary in all viewing situations are: illumination, imaging media distributed in two dimensions on a carrier, and the observer. Some conditions of each element are included among definable models. This discussion is arranged first by media, then by applicable illumination conditions, then by viewing at the best and worst angles in light and in dark surround. Final sections include typical conditions and measures for control of image appearance.