This invention relates to film printers and, more particularly, to apparatus for executing light control operations during bidirectional film transport in a printer.
Film printers are employed to expose a reel of raw film to the frames of photographic images on a reel of master film while the master film and raw film are transported together. Light control operations are commonly executed during the exposure process in high quality film copying operations. For example, red, green, and blue color corrections are made by so-called light valves at the beginning of each scene of the master film to compensate for the different lighting conditions under which the master film was produced and different film characteristics. In order to have one scene fade out and/or the next scene fade in, a fade is executed by gradually changing the intensity of the exposing light on a frame by frame basis.
Notches or RF strips on the film have been used for many years to mark the frames at which light control operations such as color corrections are to be executed. The color corrections are stored on a punched paper tape in the sequence in which they are to be made during film transport. Each time a notch or RF strip is sensed during film transport, the corresponding color correction is read from the tape and made by the light valves. The use of notches or RF strips to mark the master film is objectionable because the master film must be handled to so mark it, and, in the case of RF strips, the strips may come off the film.
Recently the technique of frame count cuing has been developed to indicate the frames at which light control operations are to be executed without marking the master film. The frames of the master film are counted during transport. The frame counts at which the light control operations are to be executed are stored on the tape with the corresponding color corrections. The frame counts on the tape are compared with the actual frame count of the master film during transport to generate cue signals that execute the color corrections at the coincidence of both.