From the point of view of the object, it is separating the region under scrutiny from the rest of the field, it is interrupting the total life of the spectacle, which assigned to each visible surface a determinate coloration, taking the light into account; from the subject's point of view, it is substituting for the comprehensive vision, in which our gaze lends itself to the whole spectacle and is permeated by it, an observation, that is, a localized vision which it controls according to its own requirements.