Cinematographic annual : 1931 (1931)

40 CINEMATOGRAPHIC ANNUAL Positive Fade-Outs. It is assumed that a fade-out is to be introduced into an editorial positive print after it has been developed and when the editing is complete. A convenient method of darkening the film so as to simulate a fade-out is to stain the film with increasing quantities of a neutral olack dye as the end of the scene is approached. A satisfactory method of controlling the density added in this way is to vary the time of bathing in an aqueous solution of a dye which has an affinity for gelatin. No single dye having the desired properties was found but a combination of three dyes in the formula given below produced a visually neutral black with a projector low-intensity arc lamp. It would be possible to use these dyes in slightly modified proportion in case the spectral distribution of the light source used was somewhat different from that mentioned. The formula can be considered merely as a guide to the proper proportions because various samples of the same dyestuff are often found to differ in purity. Visually Neutral Dye Bath Acid anthracene brown B2) 8.7 grams Toluidine blue3) 8.7 grams Naphthol green3) 2.6 grams Water to 1.0 liter In deciding upon the density to be added by dyeing, preliminary tests were made which showed that a maximum density of about 4.0 should be reached in order to obliterate the image entirely. This density seems rather high but is necessitated by the fact that the contrast is not degraded by the addition of a uniform density over the picture. It is necessary, therefore, to increase the superimposed density to a point where even the brightest part of the image is covered effectively. This condition is usually attained when the added density is 4.0 because of several factors. Among these, the following are important: (a) Visual contrast perception is greatly reduced at a screen brightness level equal to one ten-thousandth of the ordinary level. (b) The adaption level of the eye in an ordinary auditorium or theatre is usually at a level which is much higher than that which would give the best contrast perception when the fadeout is in progress. (c) The stray light falling on the screen is usually enough to obliterate the image beyond a brightness level reached during the fade. From the considerations cited previously it was concluded that a constant change in density with distance along the fade would be suitable. Tests of positive fades made in this way proved satisfactory on projection. It was found that the density produced by the dye formula given above was proportional approximately to an exponential of the time *) Grasselli. 2) Hoechst (marketed by General Dyestuffs Corp.. 23 3 Fifth Avenue, New York. N. Y.)