Re: diffraction curiosity questions

In article (info lost) someone wrote:

Of course it isn't only in optical resonators that this is true. What
most optical designers like me find extraordinary is that for an
optical system which is "useful" (in other words, not too badly
aberrated), the aberrations and hence the diffraction performance, can
be estimated through ray tracing.

Is the explanation perhaps that "useful" systems are essentially always
limited to using low spatial frequencies -- or more accurately, small
spatial frequency spreads if viewed in an appropriately chosen
coordinate system?

(since what large spatial frequency spreads do is to scatter / diffract
/ refract light at *large* angles, i.e. out of the optical system --
which is seldom useful.)

Or at least, this is another way of viewing the situation.
.

Loading