The Cine Technician (1953-1956)

166 CINE TECHNICIAN November 1955 A Technician's Notebook HIGH INTENSITY CARBONS THE increasing use in the last few years of colour negative materials balanced for use with tungsten lighting has led to the development, in the U.S.A. and in this country, of high intensity carbons which work at a colour temperature of about 3350°k, and, with the addition of a very light filter, to eliminate excess blue and ultra-violet, can be mixed with " inkies " in photographing colour films with tripack stocks or the Technicolor low-light process. Howard Cricks, in the " Kine Weekly," and Charles Handley, of the National Carbon Co., in the " American Cinematographer," have written about what is being done in this field on both sides of the Atlantic. As far as one can judge from these reports the Morgan Crucible Co., responsible for the development work here, have kept level with, if not rather ahead of, their competitor in the States. For example, according to the " American Cinematographer " article the new carbons have so far been developed for use in the " Brute," and yellow flame carbons are planned for the 150-amp. Type MR-170 lamp, while over here, apparently, the new carbons are available in trims suitable for the " Brute," the MR-170, the MR-90 and the DuArc. To return to the reasons for these new developments — Handley remarks that though a white light source composed of equal parts of red, green and blue, lends itself to easier control when removal of one colour component is indicated, incandescent tungsten has certain advantages in cinematography. Apparently it is possible to balance BY A. E. JEAKINS colour film to tungsten lighting at a higher speed rating than if a white light balance were used. Converting white light to a tungsten balance by filtering an arc burning standard carbons would produce a loss of 40%. For instance, a " Brute " burning standard carbons would require an MT-2 plus a Y-l filter. Changing to yellow flame carbons the MT-2 filter is eliminated. The arc has two great advantages in the studio over other light sources, namely a very large amount of light from one unit, and small source size, which adds up to great carrying power or " punch." sharp shadows and controllability. Another advantage of the arc over the tungsten source is its relative immunity to colour changes due to voltage fluctuations. A voltage drop from 115 to 100, with a lOkW. incandescent, will show &% change in colouration; with the same drop in voltage an arc burning yellow carbons will show only 2',. So the introduction of the new yellow flame carbons has restored to the lighting cameraman an extremely valuable tool for key lighting, effect lighting, back lighting and high-level fill lighting. Cricks remarks that he is convinced that, thanks to these developments, the arc will largely supplant the " inkie " for all but the smallest colour films. Incidentally, the American practice is to use a Y-l filter on the lamps, while here Kodak have developed a light straw filter to bring the colour temperature of the arc to the standard 3,250 :K. Among the productions which have been photographed using the new carbons are Carol Reed's A Kid for Two Farthings, Moby Dick, The Ten Commandments, Kismet, and Guys and Dolls. The accompanying table showing the light output of the "Brute" at various distances and for different beam spreads with filtered white flame and yellow flame carbons is from the " American Cinematographer." Produced in experimental quantities for three years, DuPont's (Continued on page 167) 40 FEET LAMP TO SUBJECT 50 FEET LAMP TO SUBJECT 75 FEET LAMP TO SUBJECT 100 FEET LAMP TO SUBJECT Spot* dia. in Feet Intensity!; F.C. Spot* dia. in Feet Intensity] F.C. Spot* ilia. in Feet Intensity] F.C. Spot* dia. in Feet Intensity] F.C. IVhite Flame Carbon Yellow Flame Carbon White Flame Carbon Yellow Flame Carbon IVhite 1 lame Carbon Yellow Flame Carbon White Flame Carbon Yellow Flame Carbon Max. Flood 25 270 450 32 180 300 45 78 130 64 42 70 Min. Spot 3 4200 7000 4 JOO0 5000 6 1 260 2100 8 720 1200 *Spot diameter at which the intensity is 50",, of the intensity in centre of beam. | Maximum intensity in foot candles at centre of beam with lamps filtered as follows: white flame carbon — one MT-2 and one Y-l gelatine filters. yellow flame carbon — one Y-l gelatine filter.