Abstract: In an equivalent tone region detecting device, a position on a color picture is specified, so that video signals are provided separately according to the tricolor hues for the specified position through a scanning operation with a television camera, and similarly video signals are provided for another position through the succeeding scanning operation. The former and latter video signals are compared with one another, respectively, to determine whether or not the tone of the second position is equivalent to that of the specified position, whereby a region which is equal in tone to the specified position is detected.

Abstract: An improved web infeed system feeds a web of material to printing plate roll having a tension sensor, a compact differential drive unit and a dancer roll mechanism. A main rotation input is imparted from a drive motor to the flexible spline while a portion of main rotation input is imparted via a clutch to the wave generator in the direction opposite to the rotation of the flexible spline, and the result of computing said two rotation inputs is obtained from the circular spline to produce an output, then the state of engagement between the clutch and output is changed by a controller which computes the signal of a tension sensor in a place advance circuit, thereby controlling the rotation speed of said output to maintain constant the tension of the web.