The Cine Technician (1939)

March-April, PJ38 T II CINE-TECHNICIAN 224 Technical Abstracts Some Lighting Problems in Colour Cinematography -WHY NOT LET IS KNOW WHAT IT IS '.' T. T. Baker. In additive processes the primaries are generally blue-violet, green, and organge spectral bands, which arc not narrow and which overlap to some extent. The exposure latitude of a colour-screen process is less than that black-and-white negative stock. Under-exposures often tend towards excessive blue, and over-exposures toward some other predominant colour, due in some measure to differences in the foot and shoulder of the characteristic curves of the emulsion when exposed to the three primary bands. Over-exposure results in dilution oi the colours due to invasion of each primary into its neighbour's territory. There is thus a colour-saturation latitude in the screen or matrix, distinct from a true emulsion latitude. The object here is to discuss a method of calculating the approximate range of studio light-intensity that will preserve the best colour balance of which any particular additive process may be capable. For Dufaycolor film, a widge spectrogram of suitable steepness is made representing average exposure, such as from a density of 0 to 2.5. Upon development and reversal, the peaks throughout the wedge spectrum arc shown as completely saturated (i.e., I'll) per cent of the reseau or matric saturation). But as any spectral zone is followed downward from the peak, the colour becomes diluted and may become even white as the image approaches the base line, and, therefore, maximum exposure. This is caused by the fact that , upon over-exposure, scattering carries the light behind (say) a green element into the region of neighbouring blue and red elements, so that the resulting colour is reseau-green plus some blue and red, or rescau-grcen plus white. The effect is accentuated in reseau composed <>t less saturated colour elements. By measuring from the peak to the position on any ordinate where distinct dilution becomes apparent, the permissable range of light intensity on the set can be computed from the difference of the log opacites of the two points on the ordinate. (Journal oi the Society of Motion Picture Engineers) Development and Resolving Power of Photographic Negatives A. Charriou and S. Valette. Bull. soc. franc. Phot. , lorjf : 64-75. Using both microscopic examination of the negative and enlargement in a special optical system as means of measurement, resolution was found to increase with exposure, reach a maximum value, and then decrease. One orthochromatic and three panchromatic emulsions were compared in the following developers: (1) a typical clou formula; (2) elon-hj droipiinoiie ; (3) the "14-2" buffered borax; (4) an M-Q formula containing fchiosulphate ; (5) an elon-glycin-PPD ; and (6) an elon PDD-phospate. Tables show the differences in resolving power obtained with variations in exposure and development, contrast, emulsion speeds, and resolving power. The buffered borax developer was found fcoj give both maximum emulsion speed and highest resolving power, but yielded to low contrast for the aerial work under consideration. K.W .11. I Bulletin issued bj Kodak Research Laboratot Production of Fine-Grain Images hy Development Followed by Intensification A. Seyewetz. Bull. soc. Franc. Phot. , (3)24: 45-7. Ordinary intensification enlarges the grains, and hence is not suitable for fine-grain work. Intensification by dyeing, which consists in the fixing to the grain oi a dark dye, does not possess this drawback. "Chromorenl'orcateur Lumiere", which is composed of a mixture of red, blue and yellow in proportions that yield an almost neutral tint, is suggested for the purpose. The silver image must first be transformed superficially into silver thiocyanate-cuprous thiocyanate by treatment with a copper sulphate-ammonium thiocyanate solution. The intensification may be applied to images of very fine grain, but too low in density and contrast to be suitable for enlargng. An amino-napthal sulphonic acid (1,2,4) — trisodiuni phosphate developer is recommended for the initial development. The results obtained by intensification are comparable in graininess to those obtained with the best available tine-grain developers, and possess the advantage of having better detail in the low exposure parts and better gradation.— T.H.J. (Bulletin issued by Kodak Research Laboratories) Standard Nomenclature for Release Print Sound Tracks As a further step in the programme of co-ordination between studio and theatre, the Research Council of the Academy of Motion Picture Arts and Sciences recently undertook to standardise the nomenclature for release print sound tracks, particularly as developments in sound recording equipment and technique have recently led to the appearance in the theatre field of a number of various new and different types of sound track. The Standard Nomenclature for Release Print Sound Tracks follows, with examples of each type included. (Besearch Council Academy of .Motion Picture Arts and Sciences). A New Reel-End Alarm l». Canady and V. A. Welman. •/. Soc. Mot. Fie. Eh,,., 28: 314-17, March, L937. A photo-electrically actuated reel-end alarm for projectionists operates within two or throe layers of film of the predetermined setting. Kodak Bulletin