Patent GB-693823-A (GB)
Title: Improvements in or relating to composite photography
IPC: G03B33/00
Filed: 1949-06-01
Abstract: 693,823. Composite photography. TECHNICOLOR MOTION PICTURE CORPORATION. June 1, 1949 [June 30, 1948], No. 14685/49. Class 98 (ii). In a method of separately printing the background and foreground pictures on to a cinematograph film there is used a mask proper having one portion clear and the other opaque and a master film having a picture in the portion corresponding to the opaque portion of the mask proper and having the outer portion thereof clear, the master film is formed by printing through an auxiliary mask having clear and opaque areas corresponding to those of the mask proper, both the master film and the auxiliary mask are made on low contrast stock in which the silver in the opaque portion of each tends to spread across the boundary between the opaque and clear portions, and the auxiliary mask and master film are so exposed and developed that spreading of the silver in one substantially counteracts the spreading of the silver in the other. In another method the mask proper is composed of two component masks, both of which are clear in one of the portions and opaque in the other, and the component masks are made by exposures and developments which are not excessive enough to cause the silver to spread across the boundary between the portions of each mask and thereby to destroy the fine detail along said boundary. One embodiment is described in which both methods are used in conjunction in the production of a composite colour film. As shown in Fig. 2, a foreground scene FG is illuminated with white light from a lamp L and a plain backing D is illuminated with white light from a lamp L and a plain backing D is illuminated by light from mercury vapour lamps BG and passing through a filter F transmitting only green light, as described in Specification 693,889. The scene and backing are photographed by a camera of the kind described in Specification 382,239 and including a beam splitter P and two film gates in front of which are positioned a green filter G and a minus green filter MG respectively. A green-sensitive film FNg is fed through the gate associated with the green filter and a tri-pack consisting of a redsensitive layer FNr and a blue-sensitive layer FNb is fed through the other gate. Thus, the backing D is exposed only on film FNg and gives rise to a substantially opaque area on the film when it is developed. A positive print FMb, FMg, FMr of each record is taken and developed. Another positive FPg of the green record is made and is placed in superposition with the negative FNb to produce three background masks, two of these masks M1 and M2 being formed on high contrast stock and the other M3 on low contrast stock. During development of mask M3, the silver along the border line between the heavily overexposed background area and the unexposed foreground area grows into the latter area. Colour separation negatives BNb, BNg, BNr of a background scene are now formed and positives printed therefrom on low contrast stock and then superposed in turn on mask M3 and exposed again to form background master positives BMb, BMg, BMr. During development, the silver along the border-line between the heavily overexposed foreground area and the background area tends to grow into the latter area and so counteract the growth which occurred during development of mask M3. Hence, the opaque area on each background film BMb, BMg, BMr is equal in size to the image on each of the foreground negatives FNb, FNg and FNr. The next step is to expose light-sensitive films to light from the foreground positions FMh, FMg, FMr, in each printing operation placing mask M1 in contact with the light-sensitive film and mask M2 in contact with the positive. Because of the masks, each of the light-sensitive films remains unexposed in the background area thereof. Each film is then exposed to light through the corresponding background positive to produce three colour separation records CDb, CDg, CDr of the background and foreground. By means of an imbibition dye printing process, for example, the final composite film in natural colours is produced.