Photosite
A single light-collecting element on a sensor, corresponding to one pixel in the final image.
Measured in
µm
In depth
A photosite is a well that accumulates electrons freed by incoming photons, and it is colour-blind — its colour identity comes from the filter placed over it. It is not literally a pixel: a raw file's pixel is reconstructed from a photosite's own reading plus estimates borrowed from its neighbours during demosaicing.
Examples in practice
A 24-megapixel full-frame sensor has 24 million photosites, each about 6 µm across.