Oblique imaging, magnification and image intensity

Some of the usual approximations used for normal non-oblique imaging become inaccurate or unusable for very oblique imaging situations, especially at low f-numbers. Image brightness and magnification are calculated for isotro pic surfaces which are accurate for extreme angles. An analytical descripti on without approximations of the off-axis case is derived, which at its lim its reduces to the expected equations for small angles and apertures. It is shown that lenses that perform well in normal perpendicular imaging also p erform well in oblique imaging applications.