Summary Under two adaptation conditions (dark and light), are shown simple shapes whose presentation duration, luminance and size vary. Observers estimate, using interval scales, two sensory dimensions of one and the same stimulus (brightness and sharpness). For brightness of light stimuli standard facts are obtained : temporal summation up to a critical duration as a function of stimulus luminance, absence of area effect. In the case of sharpness, the terms are different : temporal summation takes place up to shorter critical durations, and stimulus size plays a part in the enhancement of contour. This spatial factor intervenes in a similar way in the case of dark stimuli, at the moment of light-adaptation. These results show that the physical variables of time and space are used simul-taneously in different ways by the visual system and support the hypothesis of parallel treatment.