Marginal Ray

The marginal ray is the ray that travels from the center of the object, to the edge of the entrance pupil, and on to the image surface.

If there is vignetting, OpticStudio extends this definition by defining the marginal ray to be at the edge of the vignetted entrance pupil. If ray aiming is on, then the marginal ray is at the edge of the vignetted stop.

See also the definition of the Chief Ray.