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Chapter 10 - Lighting:
|A Random Illusion
Courtesy of Illusion-Optical.com
In connection with lighting it should be noted that contrasts play a prominent role as they always do. These have been discussed in other chapters, but it appears advantageous to recall some of the chief features. The effect of contrast is always in the direction of still greater contrast. That is, black tends to make its surroundings white; red tends to make its surroundings blue-green (complementary), etc. The contrast-effect is greatest when the two surfaces are juxtaposed and the elimination of boundary lines of other colors (including black or white) increases its magnitude. The contrast-effect of colors is most conspicuous when there is no brightness-contrast, that is, when the two surfaces are of equal brightness and therefore differ chiefly in hue. This effect is also greatest for saturated colors. It has been stated that cold colors produce stronger contrast-effects than warm colors, but experimental evidence is not sufficiently plentiful and dependable to verify this statement.
As the intensity of illumination increases, colors appear to become less saturated. For example, a perfectly red object seen under the bright sun at noon is like to be painted by an artist as an orange-red because it does not appear as saturated as it would under a much lower intensity of illumination. In general, black and white are the final appearances of colors for respectively very low and very high brightness. As the intensity of illumination decreases, hue finally disappears and with continued decrease the color approaches black. Conversely, as the intensity of illumination increases, a color becomes apparently less and less saturated and tends toward white. For example, on viewing the sun through a colored glass the sun appears of a much less saturated color than the haze near the sun or a white object illuminated by sunlight.
Visual adaptation also plays a prominent part, and it may be stated that all sensations of light tend toward a middle gray and all sensations of color tend toward neutrality or a complete disappearance of hue. The tendency of sensations of light toward a middle gray is not as easily recognized as changes in color but various facts support this conclusion. In lighting it is important to recognize the tendency of color toward neutrality. For example, a warm yellow light soon disappears as a hue and only its subtle influence is left; however, a yellow vase still appears yellow because it is contrasted with objects of other colors. In the case of colored light the light falls upon everything visible, and if there is no other light-source of another color with which to contrast it, its color appears gradually to fade. This is an excellent example of the tremendous power and importance of contrast. It is the life of color and it must be fully appreciated if the potentiality of lighting is to be drawn upon as it should be.
Physical measurements are as essential in lighting as in other phases of human endeavor for forming a solid foundation, but in all these activities where visual perception plays an important part judgment is finally the means for appraisal. Wherever the psychological aspect is prominent physical measurements are likely to be misleading if they do not agree with mental appraisals. Of course the physical measurements should be made and accumulated but they should be considered not alone but in connection with psychological effects.
The photometer may show a very adequate intensity of illumination; nevertheless seeing may be unsatisfactory or even impossible. An illumination of a few foot-candles under proper conditions at a given surface is quite adequate for reading; however, this surface may appear quite dark if the surroundings are bright enough. In such a case the photometer yielded results quite likely to be misinterpreted as satisfactory. It should be obvious that many optical illusions discussed in preceding chapters are of interest in this connection.
An interesting example of the illusion of color may be easily demonstrated by means of a yellow filter. For this purpose a canary glass is quite satisfactory. When such a filter is placed before the eyes a daytime scene outdoors, for example, is likely to appear to be illuminated to a greater intensity than when the eyes are not looking through the filter. This is true for a glass used by the author notwithstanding the fact that the filter transmits only about one-half as much light as a perfectly clear colorless glass. In other words, the brightnesses of objects in the scene are reduced on the average about fifty per cent, still the subject is impressed with an apparent increase in the intensity of illumination (and in brightness) when the filter is placed before the eyes. Of course, the actual reduction in brightness depends upon the color of the object.
In such a case as the foregoing, true explanations are likely to involve many factors. For this reason explanations are usually tedious if they are to be sufficiently qualified to be reasonably near completeness. In this case it appears that the yellow filter may cause one to appraise the intensity of illumination as having increased, by associating such an influence as the sun coming out from behind a cloud. If we look into the depths where light and color accumulated their psychological powers, we are confronted on every hand by associations many of which are more or less obscure, and therefore are subtly influential.
The psychological powers of colors could have been discussed more generally in the preceding chapter, but inasmuch as they can be demonstrated more effectively by lighting (and after all the effect is one of light in any case) they will be discussed briefly here. They have been presented more at length elsewhere.
It is well known that the artist, decorator, and others speak of warm and cold colors, and these effects have a firm psychological foundation. For example, if a certain room be illuminated by means of blue light, it does seem colder. A theater illuminated by means of bluish light seems considerably cooler to the audience than is indicated by the thermometer. If this lighting is resorted to in the summer time the theater will be more inviting and, after all, in such a case it makes little difference what the thermometer indicates. The "cold" light has produced an illusion of coolness. Similarly "warm" light, such as yellow or orange, is responsible for the opposite feeling and it is easily demonstrated that an illusion of higher temperature may be produced by its use. As already stated, color-schemes in the decorations and furnishings produce similar effects but in general they are more powerful when the primary light is colored. In the latter case no object is overlooked for even the hands and faces of the beings in the room are colored by the light. In the case of color-schemes not all objects are tinged with the desired "warm" or "cold" color.
In the foregoing, associations play a prominent role. The sky has been blue throughout the numberless centuries during which the human organism evolved. The blue-sky during all these centuries has tinged the shadows outdoors a bluish color. That shade is relatively cool we know by experience and perhaps we associate coolness or cold with the aerial realm. These are glimpses of influences which have cooperated toward creating the psychological effect of coldness in the case of bluish light. By contrast with skylight, sunlight is yellowish, and a place in the sun is relatively warm. South rooms are usually warmer than north rooms in this hemisphere when artificial heat is absent and the psychological effect of warmth has naturally grown out of these and similar influences.
We could go further into the psychology of light and color and conjecture regarding effects directly attributable to color, such as excitement, depression, and tranquility. In so doing we would be led far astray from illusions in the sense of the term as used here. Although this term as used here is still somewhat restricted, it is broader in scope than in its usual applications. However, it is not broad enough to lead far into the many devious highways and byways of light and color. If we did make these excursions we would find associations almost universally answering the questions. The question would arise as to innate powers of colors and we would find ourselves wondering if all these powers were acquired (through associations) and whether or not some were innate. And after many interesting views of the intricate subject we would likely conclude that the question of the innateness of some of the powers of color must be left unanswered.
As an example let us take the case of the restfulness or depression due to blue. We note that the blue sky is quite serene or tranquil and we find that the delicate sensibilities of poets verify this impression. This association could account for the impression or feeling of tranquility associated with blue. On proceeding further, we would find nature's solitudes often tinged with the blue skylight, for these solitudes are usually in the shade. Thus their restfulness or even depressiveness may be accounted for - partially at least. These brief glimpses are presented in order that they may suggest to the reader another trend of thought when certain illusions of light and color are held up for analysis. Besides these our individual experiences which have molded our likes and dislikes must be taken into account. This phase of light and color has been treated elsewhere. [The Language of Color, 1918, M. Luckiesh.]
Chapter 10 - Lighting:
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Chapter 10 - Lighting:|
The Apparent Ending of a Searchlight Beam
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