Proceedings of the British Kinematograph Society (1931)

effect on development shown in the next diagram. Here we see a family of H. and D. curves for six times the development. The gamma rises with increasing time of development up to a point, after which the maximum black having developed, the shadows continue to develop, the result being that the gamma slightly decreases. This characteristic of our emulsion is a valuable one to the producer. The effect of the gelatin /silver ratio on time of development is seen in the diagram. In conclusion I would like to draw attention to the question of illumination. It looked some time ago as though halfwatt lamps would come into general use in view of the talking picture, but itis generally agreed that sufficient life and modelling cannot be got into the photograph without the use of arcs, quite apart from the question of heat. Arclamps, especially high intensity ones, are usually employed the carbons of which are either cored or impregnated with metallic salts. Either core or impregnation necessarily tints the flame, and here arises a new point of difficulty in standardisation in colour kinematography. A camera man who knows his studio, and who knows the spectroscopic composition of his various light units, can by computation, or trial and error even, correct the falseness of his light in the studio. But a thing which we have found rather disconcerting is that a film in natural colours which appears absolutely perfect when projected in one theatre will look too bluish, or too greenish, or perhaps too yellow in another one, and on investigating the distribution of spectral emission of various makes of carbons used in projectors in London and elsewhere, we find a very alarming difference in the colour of the flame given. This is a point to which I would draw urgent attention, as in the event of natural colour films becoming very general, as I feel convinced they will do, some standard source of white hght will have to be adopted in the theatre for projection. This completes what I have to say on the production of the film, and we will now see some of the results on the screen. THE SPICER-DUFAY COLOUR PROCESS QUESTIONS. Mr. VINTEN : I would like to know why the lines are run diagonally across the film instead of in the direction of the film. Mr. THORNE BAKER: It is the result of a great deal of experiment. We have found from practical observation that by having one line at 67° and the other at 23° we get the least visibility of the matrix from the nearer seats in the theatre. Mr. VINTEN : It gives one the impression that the lines run across the sheet against a particular coloured subject and rather looks as if it tends to exaggerate the lines. Mr. THORNE BAKER: The pictures I have shown with the exception of the boys in the swimming pool are 30. to the m.m. ; the boys were 36 to the m.m., and we have now got up to 40 to the m.m. Mr. VINTEN: The pool certainly was a superior picture from here. Could we have the opinion of somebody at the back of the room. Mr. EVELvetIGH : I wasin that position, and when I got past the table on which the lantern is I lost the lines altogether. Mr..THORNE BAKER: Our general experience in London theatres is that after the sixth row of the stalls the lines are quite invisible. Mr. HopGson: Can Mr. Thorne Baker tell us which were originals and which reproductions ? Mr. THORNE BAKER: About one-third of the pictures were copies and about two-thirds originals. I do not think it is fair at this stage to make a run, as we have to-day, of original and copy one after the other. The reel you have seen is an indiscriminate mixture of originals and copies. We can get any number of copies. In many colour processes, if you make 50 copies there is a certain variation in the results, but that variation does not exist in this process.