Home Movies (Jan-Dec 1941)

CELLULOID BASE \ CELLULOID BASE ^EMULblON HALATION AREA LIGHT RAY ANTI HALATION BACKING .■= EMULSION LIGHT RAY POSITIVE FILM REVERSAL FILM llluslrating principle of halation, inherent characteristic of positive film. Compared is cross section of reversal film with protective, halation-absorbing backing. HOME MOVIES FOR MARCH Authored by George Witherow csCimiiationd yposmvi / Mm . . . cl6 a reverSa JVI.OVIE amateurs have long awaited the day when an inexpensive film comparable in price to positive would be made available for home processing which would contain more of the characteristics of panchromatic film. In the meantime, the unorthodox use of positive as a “reversal” film continues among hundreds of home-processing amateurs and not without some measure of suc cess. There are, of course, many who have not fared so well. • Reproduced below is on enlargement from Amateurs about to Venture into use and home frame of 16mm positive film developed by reversal process. Although background registered normally, sun-tanned bathers photographed black. To obtain any kind of detail in the figures, it would have been necessary to open up the lens to a point where background registered in solid white and without any detail whatever. reversal of positive film quite naturally will ask: “What success may I expect?” “What precautions are necessary to insure a measure of success?” Positive film, as most movie amateurs know, was originally conceived for the purpose of making positive projection prints from negative films. Essentially, negative is the “camera” film and positive, the “projection” film. More recently, however, exploring amateurs discovered positive film could be used as a negative — that is, as a reversal film — under certain limited conditions. The important difference between positive and negative film (the latter term, in this instance, being synonymous with panchromatic reversal films) is that positive lacks the color sensitivity of panchromatic ; lacks speed, thus requiring increased exposure which many lenses such as the f/3.5’s are not always able to give ; and no less important — is not protected with an anti-halation back ing. Favoring positive film is the fact it is far less expensive than panchromatic; it can be handled during processing under a brighter safelight ; and it is finer grained. Positive film possesses very little latitude. Latitude, in the language of photography, means the ability of a film to record an extreme tonal range. If a film is capable of recording only a limited range of color tones, tones outside the range will record opaque or chalky. If exposure is set for the lower tones, the higher tones become “washed out” or transparent, resulting in virtual over-exposure for the high tones, normal exposure for the low. The reverse would be true were exposure set to favor the higher tones. When we say positive film lacks color sensitivity or is “color blind,” we mean the emulsion of this film is sensitive only to ultra-violet, blue, and some green. It is not sensitive to yellow-greens, nor to yellow, orange, or red. Positive film will record red roses or tulips in black or muddy gray. Yellow, dark green, orange, or red objects will photograph quite dark, if not absolutely black. Blue objects, including skies, will record extremely light, and dark-skinned persons or those with a sun-tan will photograph unnaturally dark. The emulsion speed of positive film is slow. In fact, it is probably the slowest movie film obtainable except for some special emulsions designed for critical experimental work. The average exposure for this film in bright sunlight is f/6.3, which practically restricts its use to bright, sunny days. Scenes have been successfully filmed with positive on cloudy days at f/3.5. The red light of late afternoon calls a halt to the user of positive film unless his camera is equipped with an f/1.9 lens. Since positive film tends to be contrasty, due to its slow speed and poor latitude, subjects of limited tonal range will photograph best. This would include subjects flat lighted on cloudy days, with few if any shadows or dark areas. On the other hand, scenes in bright sunlight will record in heavy opaque and chalky white tones. If one were to use positive film in the camera strictly as a negative, the photographic result • Continued on Page 144 116