In a camera, light bounces from a light source, off an object, into receptor, with at least one aperture in the path to ensure that light arriving from differen

In a camera, light bounces from a light source, off an object, into receptor, with at least one aperture in the path to ensure that light arriving from different directions reaches different sensors. These sensors collect light from some area over time which can be recovered as information (chemically or electrically). Light passing through an aperture is subject to diffraction (which rules out a perfect square beam of light) and possibly other distortions, and the sensor may or may not be a perfect, uniform square, but in any case it's all equivalent to a perfect point in space that receives undistorted, refractionless light then applies a filter and integrates it over time and area. The underlying physical phenomenon that allows integration to happen is the ability for a film grain or ccd cell to count up incoming photons. These ideal sensors may be arranged on a grid, but the filter that maps source light to sensor value won't look anything like non-overlapping square boxes.