The angle in radians apply at any distance - if I understand correctly it is about when light from two adjacent points would have to "hit" the aperture so close

The angle in radians apply at any distance - if I understand correctly it is about when light from two adjacent points would have to "hit" the aperture so close as to interference with each other. Another random link from the Internet makes the connection between the definition of 20/20 vision and Rayleigh limit: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/Raylei.html http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/Raylei.htm...