Exposure control for cinematographic films using telecine apparatus

#This invention relates to the use of telecine apparatus for controlling the exposure of cinematographic, i.e. motion picture, films.

#The shooting and developing of cinematographic film is a highly artistic process, with many adjustments being made during production in order to result in an end product of optimal quality. One of the aspects that requires control is the exposure of the film.

#The variables that contribute to the lightness or darkness of exposed processed film include the following:

#The above and other features and advantages of the invention may be more readily understood by reference to the following description of preferred embodiment taken in conjunction with the accompanying drawings, in which:

#FIG. 1 shows schematically the use of a telecine machine and controller to produce an exposure log in accordance with the invention;

#FIG. 2 shows schematically how the exposure log can be used to provide exposure compensation in the printing of positive film;

#Referring to FIG. 1, a telecine machine 1 has reels 2 and 3 carrying exposed negative cinematographic film 4. Frames of the film are scanned by a flying spot CRT tube 5 and the light is analysed by a unit 6 which detects the red, green and blue components using optical transducers in a conventional manner. The telecine machine 1 produces a video output which is fed along a line 7 to a video monitor 8 for viewing by an operator. The telecine 1 may be of a type such as the URSA or URSA Gold manufactured by Cintel International Limited in Ware, England or the FDL90 manufactured by BTS in Darmstadt, Germany. The video signals may also be transmitted to a storage device, such as a video recorder, for storage on video tape or disc or other suitable media.

#The telecine 1 is controlled by a controller 9 having controls 10 for operation by a user having regard to the image displayed on the monitor 8. The controller 9 sends control data via channel 11 to the telecine 1, and sends synchronisation data in the form of timecode to the telecine 1 via channel 12. The film will generally contain its own synchronisation data or timecode (also known as filmcode or keycode) and the timecode for the entire system may be based on this data. Alternatively, the timecode for the system may be generated in the controller 9 and passed to the telecine 1. In either case, the timecode generates a unique identification value for each frame of the film which is consistent throughout the whole system.

#The control signals passed to the telecine 1 from the controller 9 include the following parameters: Master Gain; Master Lift; Master Gamma; Differential Gain; Differential Lift; Differential Gamma; and Secondary corrections of each of the Red, Green or Blue content of each of the Red, Green, Blue, Cyan, Magenta and Yellow channels. The adjustment of these various parameters by the operator of the controller 9, using the controls 10, with reference to the representation of the film image displayed on the monitor 8 produces a resultant electrical image of optimum quality from the image stored on the exposed negative cinematographic film 4.