Abstract: An electron - optical - photographic system utilizes the novel qualities of an optical density wedge filter for use with a CRT oscillograph having an optical density along the taper of the wedge equal to the square root of the probability density distribution of a random variable, e.g., "white noise" displayed on one side of the X-axis of the oscillograph. The visual portrayal of the amplitude-time presentation of noise (as on a cathode ray tube) is modified by the filter to produce a uniform gray pattern. Addition of a sinusoidal signal to the noise then results in a clear recognition of the signal even when it is well below the noise level.