162 PHOTOGRAPHY IN THE COLORS OF NATURE. 



to the white grouud. In order to obtain colors that would appear 

 brighter in ordinary white light, dyes may be used which completely 

 absorb only rays that excite chiefly single primary sensations and other 

 rays in due proportion. The dyes i)roposed by me also fulfil this 

 requirement, so that even in ordinary white light the degradation of a 

 color is insignificant except in the greens, where it is noticeable. 



I have seen some of the results produced by the older process of 

 composite helichromy, and others who have also seen them will I am 

 sure bear me out when I say that the colors have invariably been 

 not only untrue, but either very dull or else flat and patchy and want- 

 ing in the delicate details and gradations of light and shade which 

 characterize good monochrome photographs. All that showed bright 

 colors resembled nothing so nuich as cheap chromos. In the compo- 

 site heliochromes by my i)rocess, which I show to-night, the colors 

 are, as you can see, as perfect in detail and gradation as the mono- 

 chrome shades of an ordinary photograph. - - - 



In photochromy it is only necessary for the photographer to make one 

 negative of the object to be re-produced, and this negative contains a 

 register of form and Hght and shade only. Coniposite heliochromy can 

 not be carried out with less than three negatives, which must contain 

 a register not only of form and light and sluide, but of color also. In 

 photochromy an artist is employed to regulate the distribution of col- 

 ors, at'cording to his taste or judgment; in composite heliochromy it is 

 the light itself which regulates their distribution and combination, 

 automatically, according to fixed and true scientific i)rinciples. Photo- 

 chromy is an art; comi)Osite heliochromy a science. - - - 



In conclusion I will say that in order to carry out the process in 

 strict accordance with the theoretical reijuirements, means must be 

 employed not only to secure three negatives and three x)rints, each of 

 which is correct by itself, but each must bear also a certain deflnite 

 relation to the others. A very little over or under exposure of any 

 one color print, or a vei-y little too much oi' too little of the color stuff 

 in the film, will change the shade of delicate colors. Fortunately, 

 there is a simple optical test by which such a defect can be detected 

 without reference to, or knowledge of, the colors of the object i)hoto- 

 graphed; but at present it is diflicult to secure such harmony of ])arts 

 when but little time can be spared to devote to the operation of the 

 process. Composite heliochromy nuist always remain a comparatively 

 costly process when carried out in a manner calculated to yield the finest 

 results, and can most profitably be brought before the public in the 

 form of optical lantern lecture illustrations, not Avith the triple lan- 

 tern, but with transparent colorprint helio-chromes mounted as lan- 

 tern slides. 



