Abstract: A lighting sensor is provided including a sleeve made from a translucent erial having a bottom intended to be exposed to the light whose illumination it is desired to measure, an optoelectronic component positioned inside the sleeve with its sensitive face disposed in line with said bottom and means for securing said component and said sleeve together.The invention overcomes in a simple way the problems due to the non linearity of the signal delivered by the optoelectronic component to the saturation of this component and to the narrowness of its aperture angle.

Abstract: A gamma correction method and device are provided for multichrome cathode y tubes, including, for each of the n-1 electron guns of the tube, a correction circuit adapted for raising the cathode modulation of this gun to a power .gamma.ref/.gamma..sub.i in which the term .gamma..sub.ref is the gamma exponent of the nth gun which is taken as reference and the term .gamma..sub.i is the gamma exponent of the gun considered. With this device the chromaticity of the colors displayed on the screen are conserved throughout the whole contrast dynamics of the tube.