British Kinematography (1949)

In duplicating an integral tripack original, the possibility of obtaining an improvement, by the use of one or more masks, is very considerable. Generally two masks will be made, one to improve colour reproduction and control contrast, and the other to control the tone reproduction of the highlights. Since a mask is simply a negative or a positive image which is either placed in contact with, or optically registered with, the colour original during the printing operation, it is obvious that a high degree of accuracy is required in the contact or optical printers which are to be used. Such a printer has been made by Irving Dyatt, and is now handled by Chroma-Tech Motion Picture Laboratories in Hollywood. Although the Chroma-Tech printer appears to be capable of dealing with a great variety of optical work, its particular advantage in the duplication of Kodachrome lies in the fact that any mask can be run through one gate, while a colour original is running through the other gate in contact with the duplicating stock. The Chroma-Tech Laboratories appear to be the only organisation claiming to make Kodachrome release prints via intermediate colour positives8, and although there is no direct evidence to support the supposition, it is probable that they are employing a positive mask which has itself been obtained by printing through what can be described asa" highlight mask." When reproducing a transparency, the lightest parts of the image fall upon the toe of the characteristic curve and will therefore be considerably " compressed." This form of tone distortion can be counteracted by making a negative mask from the original transparency in such a way that the highlights alone are recorded on the mask — the exposure being insufficient to record either the middle or the shadow tones. This " highlight " mask is next combined in register with the original, while a second or " monochrome negative mask " is made from the pair9. The second mask will usually be made by exposure through a red filter so that very little additional density will be added to any blue or green areas of the original, while some density is added to the reds. The reduction in contrast, due to the mask, can be regained when making the duplicates by using Type A material in place of Duplicating stock. Such a procedure would result in the increased saturation of all colours. Whether the Kodachrome prints which are made by the comparatively elaborate procedure which seems to be employed by Chroma-Tech Laboratories are as good as, or better than, straight contact printer duplicates, we do not know, but it is certain that other advantages do result from the method. In the first place, the colour original is protected from risk of damage and, furthermore, many optical effects can be introduced during the making of the intermediate positive. Kodachrome Sound It would only be possible to hazard a guess at the procedure which is now followed by Kodak to procure a track image in silver iodide, silver sulphide, or metallic silver, and since the outside laboratory is never likely to be responsible for Kodachrome processing, it will be 'sufficient to fsay that whatever method is employed, it results in a satisfactory image which is either silver or some salt of silver, and which is principally located in the outermost — and therefore the sharpest— image layer. Up to the present, sound has been printed on to Kodachrome from a positive, in order to comply with reversal processing, but it has recently been reported that Kodak have a patent which will allow the track to be printed from a negative10. The procedure is to print the track from a negative, and to develop the film to produce negative silver images in the picture