Perceived Visual Angle

Perceived visual angle is the subjective counterpart of the physical visual angle, the angle that a viewed object subtends at the eye. In many situations the angular size an object appears to occupy differs from its true physical angle, an effect known as a visual angle illusion or angular size illusion. The illusion shows up most clearly as a relative angular size illusion, in which two objects that subtend exactly the same physical visual angle nonetheless look like they have different angular sizes, as if their equal-sized images on the retina were being read out by the visual system as though they were different sizes. Researchers use the concept of a perceived visual angle to explain a range of well known size illusions in which context, distance cues or surrounding shapes distort how large an object seems. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/