Details of exhibit

Exhibition:
1907 Fifty-second Annual Exhibition of the Royal Photographic Society of Great Britain  
Exhibit title:
New-process photographic copies of diffraction gratings. Freak diffractor (viewing device) and ten small mounted gratings giving anomalous dispersion. Larger gratings giving normal spectra, crossed gratings, &c.  
Exhibitor:
Frederick E. Ives 
Section:
Scientific and Technical Photography and its Application to Processes of Reproduction 
Exhibit No.:
513 
Description:
(1) Made with fish glue and bichromate instead of gelatine bichromate. Glass coated with automatic mechanical whirier, coating spread and dried face down over hot plate, thus securing evenness and perfect control of thickness of film. Exposed immediately, so that there is none of the characteristic time change observed with cold dried gelatine bichromate. Exposed sufficiently to render the film entirely insoluble, so that the grating lines are kinks and not wash-out relief lines. Developed in very hot water, to make the kink strong, and also prevent markings due to clinging cold water in drying. Copies can thus be made from comparatively weak original rulings, which are many times more vigorous than the originals, up to about 8,000 lines to the inch.
(2) Control of character of line effected by application of Ives’ “pinhole image” and “optical V line” principle which was the basis of his original cross-line sealed screen half-tone process of 1886. Partly also by thickness of sensitive coating. Gratings made at will, either to throw most of the light into first order, spectra or otherwise, or “freaks,” symmetrical or asymmetrical. Control not perfect, owing (1) to difficulty of securing definite even separation of original ruling from the sensitive surface; (2) and to the fact that the line is a “kink,” the form of which depends in some measure upon the physical character of the insoluble fish glue. Control most perfect on ruling not finer than 5,000 lines to the inch, and sufficient to establish a principle.

Of course, diffraction phenomena complicate the matter; but it has been assumed, apparently with justification, that with the large pencils of light used the sum of the action by diffraction approximates in result to dioptric action in larger dimensions.

The necessary conditions can be maintained over one or more inches of surface for some of the special effects, but the extremely “freaky” gratings always vary in character over extended surface, the same character reappearing at different points, where the separation of original ruling and sensitive surface has been exactly the same. 
Exhibit type:
Photograph 
Process:
[Not Listed] () 
Award:
none