Contrast correction arrangements

Claim 1

A contrast correction arrangement for use in a colour television system including a plurality of camera tubes each for producing electrical signals corresponding to a different primary colour in a scene viewed by the tubes, a colour coder for producing from said plurality of camera tubes a composite colour coded signal in accordance with a predetermined broadcasting standard, means for producing from said plurality of camera tubes a signal representative of the greatest brightness in the viewed scene, means for producing a D.C. level control signal, a multiplier for multiplying the difference between the signal representative of the greatest brightness and a first predetermined peak amplitude thereof by said control signal such that a further signal is produced which is variable in both sign and magnitude in dependence upon the departure of said signal representative of the greatest brightness from peak amplitude, a further multiplier for multiplying said further signal with the difference between said composite colour coded signal and a second predetermined amplitude so as to produce a video correction signal of sign varying in dependence upon the sign of said further signal, and a mixer for adding the video correction signal to the composite colour coded signal thereby to produce at the mixer output a video signal of compressed, normal or expanded contrast range.