The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Chromatic Triangle                                             Chromium
bromide plate is sensitive, not only to those particular portions of the spectrum designated by D and f, but also between D and F, and F and h ; and if we use colour-sensitive plates, we find considerable increase of sensitiveness to the yellowish green about e, so that those rays for which the lens is not perfectly achromatised may act, and as these rays do not form an exact image at that point where D and f meet, they may affect the silver in such a manner as to enable the developer to reduce the same ; and although such reduction would be hardly visible
Fig. 26.
to the naked eye, yet, in enlarging, the points of confusion thus caused might become visible, and give indistinctness or fuzziness.
Chromatic Triangle. See Triangle, Chromatic.
Chromatype, Chromotype. Names applied to certain bichromate processes ; the former to an old method of Mr. Ponton's in which paper was sensitised with one dram of sulphate of copper in half an ounce of water, then mixed with half an ounce of saturated solution of bichromate of potassium. After exposure it yields a brown picture on washing with nitrate of silver solution, washing alone serving for fixation. Several variations were made. The latter name was applied by Mr. Lambert to carbon points developed on collodionised glass, and stripped when dry with the full enamel lustre.
Chrome Alum. See Alum.
Chromium. A metal unimportant in the separate state, but the compounds of which are much used in | the industrial arts. The chromates M'2Cr04, and bichromates M2Cr207, when soluble, make gelatine and similar substances highly sensitive to light, the gelatine becoming insoluble. (See Carbon Processes and Artigde's Process.)