The oscilloscopic view: retinal illuminance and contrast of point and line targets

The specification of intensity of self-luminous point and line targets, such as those created on cathode-ray tubes, is discussed and methods are outlined for measuring it and deducing the resulting retinal illuminance. The calculations can be extended to the specification of contrast by combining them with the more traditional method of identifying the retinal illuminance provided by uniform backgrounds. Such values of contrast are not independent of observation distance.