The Dictionary Of Photography

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

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Chromatic Aberration
cyanine, which is blue. It is slightly soluble in water, but more so in> alcohol and ether. It has been used for sensitising plates for ortho-chromatic work, and for this purpose either ivy, parsley or blue myrtle (periwinkle) should be used. The fresh leaves should be cut up small and rubbed in a mortar, and then allowed to macerate in alcohol for 24 hours. Chlorophyll solutions do not keep well.
Chromates. See Chromium.
Chromatic Aberration. When light passes through a prism or a lens, which may be considered as formed of prisms, it is broken up or refracted into its constituent rays. If a beam of
V           Y
.Fig. 22
light, rr, strike a lens (Fig. 22) it is refracted and dispersed, and as the violet rays are bent out of their course more than the red, it is obvious that they will meet at a point nearer the lens than the red rays, as shown in the figure. Therefore, suppose we wish to get an image of the object from which RR proceeds, and place a screen at V» we shall see a violet image surrounded by rings of blue, green, orange, yellow and red. And by placing the screen at Y» we shall get a red image surrounded by orange, yellow, green, blue and violet rings, and this will be the case at each point