The Photography of Colored Objects (Google eBook)

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The Company, 1919 - Photography, Orthochromatic - 113 pages
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Page 8 - ... the distance from the crest of one wave to the crest of the next. The wave length of the light, like the velocity, varies with the medium in which the light is travelling.
Page 51 - G" filter, because an orthochromatic filter is adjusted to photograph objects in their relative luminosities as seen by the eye, and if the yellow stain is visible to the eye it will also photograph through an orthochromatic filter. If the stain be examined through the strong " G " filter there will reach the eye no light which is not yellow, and so the stain will not appear different from the white ground. Fig. 33 shows two photographs of a platinotype print which had been splashed with yellow dye...
Page 13 - Whenthe band is from 4,700 to 5,200 the colour is a sort of orange, and as the band moves into the blue-violet the orange becomes a yellow, and finally a lemon-yellow. So that if we imagine a single band to pass down the spectrum, we get a change from light sky-blue through purple, magenta, orange, and yellow, to lemon-yellow (fig. 6). Now it will be seen that there is one class of colour which does not enter at all into this series, namely, the greens. There is really no visual suggestion of green...
Page 30 - ... compensate for the extra sensitiveness of the plate to those rays. Now in removing this light the orthochromatic filter increases the necessary exposure, because if we remove those rays to which the plate is most sensitive we must compensate for it by exposing the plate for a longer time to the action of the remaining rays, and the amount of this increased exposure will clearly be dependent both on the proportion of the violet and the blue rays which are removed by the orthochromatic filter,...
Page 60 - IN no branch of photography is the reproduction of colored objects in correct monochrome of greater importance than in portraiture, and in no branch is it in greater danger of being ignored. The flesh tints, with which portrait photographers are mainly concerned, are chiefly of a reddish or yellowish nature, while the yellow and brown shades of the hair and the variety of the eye-colors, apart altogether from the clothing, cause every sitter to present a distinct problem in color reproduction.
Page 89 - It is not possible, nor is it desirable, for any filter and plate to follow either the color sensation, color mixture, or certain other calculated curves. 2. The effect of using plates having maxima, with broadbanded weak filters, is to cause a degradation of any pure color occurring in the band of insensibility; therefore plates showing gaps in the spectrum record ( erythrosine plates, eg) should not be used for the green negative. 3. Ultra-violet should not be recorded, as it will exercise a disturbing...
Page 15 - If a color is to be rendered as black as possible then it must be photographed by light which is completely absorbed by the color; that is, by light of the wave-lengths comprised within its absorption band.
Page 89 - Ultra-violet should not be recorded, as it will exercise a disturbing effect where it is recorded by colors other than blues and violets, as is the case with some browns, scarlets, and yellows, these reproducing with a distinct bluish tint. 4. As much red should be recorded as possible. 5. There should be no unrecorded gaps in the visible spectrum, for while these may not be important for certain mixed colors of pale tints, they are fatal to correct rendering of colors, the spectra of which do not...
Page 11 - ... to it, we get white light. Since white light consists of blue light, green light, and red light, green is clearly white light minus red and minus blue: and a green body is one which absorbs both red and blue. The difference between a green object and a yellow object is that the yellow object absorbs blue only, whereas the green object also absorbs most of the red light, which the yellow object reflects. We can now make clear what is meant by complementary colors.
Page 13 - If the band shifts into the yellowishgreen from 5,600 and 6,000 it will absorb a great deal of the green and none of the red, and the colour will become bluish purple; as it shifts lower in the green towards the blue this purple becomes a reddish purple, so that when the band is situated at from 5,600 to 5,200 we have what is...

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