The Cine Technician (1939)

U i.'J C I N E-TE C H X I C ] \ N ^arch-April, L938 .hi bleached out find tin dye in the emulsions destroyed at the points where silver lias developed, the quantity oi dye affected being proportional to the quantity of silver reduced at thai particular spot. (Selective (\yr bleach process). I. Instead oi using a film with three selectively sensitised and dyed emulsions, as described in Group 3 above, three similar but undyed emulsions m;i\ be used for tin same purpose, and the dyes formed during development. Tins is t.i., the new Agiacolor development process, and it is based on the fact that certain developing agents produce oxidation products during development that will couple with other chemical substances and produce insoluble dyes. A film coaled in this manner can be made sufficiently sensitive not only to be used as a printing material, but also for actual exposure in the camera. In the 16 mm. Agfacolor film, for example, the positive image is produced by a reversal process, the coloured image being formed in the second development operation by coupling certain oxidation products with the dye components present in the three emulsion layers. (Colour developer process). Subtractive colour films have proved very popular in practice. The toning processes used in conjt nction with a double-coated positive film (such as Dipo) or ordinary positive film were at one tune (1928—31) so common in America that the report of the progress committee issued by the J.S.M.P.E. in 1931 stated that in 1930 no less than l."> per cent, of the films produced in America were colour films. ( h these two-colour processes, many are no longer used (the older Technicolor, Multicolor, Photocolor, Sennettcolor, Sirius. Polychromide, Cinecolor, etc). Ufacolor Magnacolor ami Hirlicolor use Dipo film, Harriscolor, Debrie-Dascolor and Dunningcolor use normal positive film. Brewstercolor and Cinecolor are tine '-colour subtractive processes (beam-splitter cameras) which use a double-coated positive lor two images ami produce a third by an imbibition process. The new three-colour process of Technicolor has found increasing favour in America also recently in England particularly for short travel and cartoon films, although between l'.)H4 and 1936 a number of full length coloured feature films were produced by the process. Colour filter \ Lenses Lenticulor t ronl film / ; \ \ vi ii i f I I 1 i i i v B,pock [Backfflm a i ii i i i n-rr\ Sensitive to green * blue Sensitive to red Fio. 4 $gheme of the Lertficylcted Bipack System In tin recent years (since 1 '.!•'' 1 1 multi-lav er films have 'tn- into practi al use. A selective dye bleach proe. ss using triple-coated film has been used by Gasparcolor (Berlin and London) foi short cartoon films, and hi mm. amateur films are on the market which are based on the colour develop' i | i e.g ^.gfaci -lor). Judging fr m out ;ide appearance alone, the differ between additive and subtractive processes i that tli emulsion of an additive process is generally black and white, while in a subtractive process the image itself is alw a\ s coloured. As a general rule, it maj be noted that additive colour processes require considerably more light intensity in projection than subtractive processes. Nor can they usually he used in a normal projector equipped lor monochr< projection without some alteration to the optical equipment. Their treatment in the laboratory is identical with that lor hlack-and-w lute films, however, while the subtractive processes nol onlv introduce difficulties in the manufacture of the raw stock, but require also accessory laboratory equipment to earn out the dye-forming operaf i: ins. The Duplication of Colour Kilms The printing of colour films i.e., the mass pi' i t ion ol release prints imposes more or less difficult tas on the laboratory according to the original record available. In colour film practice to-day. the following originals merit consideration. 1. Two or three-colour separation negatives on one film or on separate films, with monochrome negative images (Technicolor, Bipack processes, Gasparcolor, Francita, etc. I 2. Lenticular reversal films with monochrome positive imagfcs (Siemens-Opticolor, Agfa lenticulated bipack. etc-.). 3. .Multi-lav er reversal emulsions giving coloured positive images (the new Agiacolor and Kodaehrome). In Class 1, printing, either in contact or optically done bv the ordinary methods tor black-and-white. The photographic treatment in the development ami other baths is mechanically operated as usual. The additional processes, such as the toning of Dipo films or the Technicolor rebel process, can also be done satisfactorily bv machine. The printing of such negatives on Tripo-Pilm (Silver Dye Bleach Process, Gasparcolor) b\ using intermediate Positives, presents no technical difficulties. The printing of the separation negatives on lenticular film (or other colour-screen material), or on material of the multi-layer Agiacolor type is possible in theory, but has not yet been accomplished. Turning to Class 2. the lenticular films, a hire , number of workers have attempted for years to find a satisladorv solution to the difficulties of the printing process. Theoretically a number of possibilities suggest thems dves The Opticolor process which was demonstrated recenth in the cinema l>v prints made on a special Siemens printin" machine shows one extremely interesting attempt to solve the problem. The printing of lenticular film on multi-layer material is at present still in the experimental stage. Prints from reversal originals on multi-layer material (Class 3) are theoretically possible by printing the positive original on the same type of emulsion, such as the new Agiacolor reversible film, or on lenticular reversible film. In practice, satisfactory prints have not yet been madi [Continued at foot ol next page)