When you press the shutter release on the camera, a complex sequence of events occurs, including setting the aperture in the lens, flipping up the mirror of an SLR and a lot more.

The surface figure precision of the primary mirror in a large aperture telescope is a key factor influencing the imaging quality.

This paper discusses the accuracy problem of testing a large aperture flat mirror by using stitching interferometry, and analyses the stitching accuracy in theory and experiment.