Cinematographic annual : 1930 (1930)

128 CINEMATOGRAPHIC ANNUAL tates the combination of blue violet, blue, blue green, green, yellow, orange, and red, to give us white light. When an analysis of sunlight, or daylight, and tungsten is made in an instrument which has the ability of breaking the light up into its component parts, it will be observed readily that all visible colors are present. If we by some means subtract some definite color from white light we will have left a color which is no longer white, but which is a combination of the remaining colors of the spectrum. For example, if all of the red light is removed by some means from white light, we would have as a result a bluish green light which is made up of the remaining colors. Likewise, if by some means we could remove the green light from a white light, we would, as a result, have left a color which we refer to as magenta. Furthermore, if we remove the blue and blue violet from white light we have left, as a result of the combination of the remaining colors, yellow. The means of removing these sections of light from white light is accomplished by the use of light filters and if we examine light filters by looking at white light through them, we can see that the above statements are true. So far, consideration has been given only to the effect of removing visually certain bands of color from white light. In photography, with the use of panchromatic film and filters, effectively the same results will be obtained. The human eye has a definite visibility characteristic and it is able to record all of the different wave lengths of light which are referred to as color. Naturally, only those things are colored that our eyes see colored. Panchromatic film has had incorporated in it, by chemical means, the ability to perceive most all of the colors visible to the eye. The eye sees more of one color than it does of another but panchromatic film also has that function, although the colors in preponderance visually are not the same as those most strongly recognized by panchromatic film. In other words, the color sensitivity characteristic of the eye (visibility) has its maximum in the yellow region of the spectrum. The panchromatic negative film has its maximum sensitivity in the blue violet region of the spectrum. However, the limits of visibility and sensitivity throughout the spectrum are essentially the same for the eye and the panchromatic film. However, panchromatic film has a greater extension of sensitivity at both the blue violet and red ends of the spectrum than the eye has visibility. The point to be made, however, is that the panchromatic film and the eye are similar, although not alike. In the use of filters the cameraman has the desire to accentuate some portions of the scene being photographed and to hold back other portions of the picture. For example, a yellow filter which has the power of absorbing blue, tends to lessen the effect of sky in a scene and produce a darker rendering of the sky in the print. It also allows for the exaggeration of cloud effects, due to the fact that much of the blue is being absorbed. This has the effect of producing, photographically, more contrast between the sky and the clouds in that sky. On the other hand, it might be desirable to render some red object in a scene lighter than it appears to the eye. This can be accomplished by using a filter which absorbs some of the blue and green