Chief ray angle (CRA) is the angle at which the principal ray from the lens reaches the sensor, especially toward the edges of the image. In sensor datasheets, CRA usually refers to the sensor’s expected or supported ray angle, not just a lens property by itself.

Why it matters: modern sensors use microlenses over each pixel to direct light into the photosensitive area. A sensor with 0° CRA generally has centered microlenses. A sensor designed for a higher CRA uses shifted microlenses, especially near the edges, to better accept light arriving at steeper angles.

If the lens and sensor CRA don’t match well, edge performance can suffer: reduced sensitivity, uneven brightness, and possible color shifts. This is more noticeable when light hits the sensor obliquely, such as with compact optics or some wide-angle designs where the rear of the lens sits close to the sensor. Front-side illuminated (FSI) sensors are typically more sensitive to CRA mismatch because internal metal layers can block or reflect angled rays. Back-side illuminated (BSI) sensors are generally less affected.

So, CRA affects how efficiently the sensor captures off-axis light and how well it matches the lens/optical system, especially at the image edges.