Visual illusions; their causes, characteristics and applications - Brossura

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 Excerpt: ... retina after the form of a figure becomes distinctly perceptible. 3. Emanations of decreasing intensity extend themselves outward and backward from a moving image until lost in the darkness of the background. 4. A well known form of irradiation which occurs when a surface of greater intensity enlarges itself at the expense of one of less intensity. 6. A form having many of the characteristics of the first type, but occurring only after long periods of stimulation, of the magnitude of 30 to 60 seconds or more. IX COLOR IN order to simplify the presentation of the general subject, discussions of color have been omitted in so far as possible from the preceding chapters. There are almost numberless phenomena involving color, many of which are illusions, or seemingly so. It will be obvious that many are errors of sense; some are errors of judgment; others are errors due to defects of the optical system of the eye; and many may be ascribed to certain characteristics of the visual process. It is not the intention to cover the entire field in detail; indeed, this could not be done within the confines of a large volume. However, substantial glimpses of the more important phases of color as related to illusions are presented in this chapter. In the early chapters pertaining to the eye and to vision some of the following points were necessarily touched upon, but the repetition in the paragraphs which follow is avoided as much as possible. Simultaneous Contrast--That the life of color is due to contrast is demonstrable in many ways. If a room is illuminated by deep red light, at first this color is very vivid in consciousness; however, gradually it becomes less saturated. After a half hour the color is apparently a much faded red but upon emerging from the room into o...