244 PHOTOGRAPHS IN COLORS [Ch. VII 



plate from the safelight as here recommended can cause no damage 

 (Henry Phelps Gage, Optical Department, Corning Glass Works). 



§ 380. Choice of plates and color screens. — The hints given 

 in the little manuals sent out by the manufacturers on request by 

 their patrons give excellent hints for the selection of plates and color 

 screens for a wide variety of objects. The beginner cannot do better 

 than to follow those suggestions faithfully, until his own experience 

 enables him to supplement those suggestions. Finally, of course, one 

 wishes to be able to use his own judgment. 



In general, if any color is present in the object to be photographed 

 one will have better success with isochromatic or orthochromatic 

 plates, which are sensitive to violet-blue, green, and yellow, than with 

 the ordinary plates, which are only sensitive to the violet-blue of the 

 spectrum (fig. 140-141). If the colors involved contain orange and 

 red the isochromatic plates are not adequate, and one must then 

 use panchromatic or spectrum plates, sensitive to all wave lengths 

 (fig. 142). 



For the color screen to employ, remember that color screens are 

 not of real use for ordinary plates sensitive only to violet and blue. 

 For isochromatic plates yellow color screens are very helpful for 

 reducing the excessive effect of the violet and blue (§ 367) or for cut- 

 ting them out altogether in getting contrast effects (§ 368). The same 

 is true for panchromatic plates, only here a wider range of color 

 screens can be used to get any desired contrast or compensating effect. 



Color Photography 



§ 381. Photographs in natural colors. — This has been the aim 

 of experts in photography ever since its first invention. Lately 

 methods have been devised by which surprisingly true color photo- 

 graphs have been produced. These color pictures are better adapted 

 to large objects than to those with fine details such as are observed 

 with the microscope. Still, many objects -are fairly well represented 

 in photo-micrographs. 



The author's experience in color photography has been limited 

 to the "Autochrome Process" (colored starch grain process). The 

 directions in the small manual sent out with the plates are very clear, 



