Re: Incorrect Seidel aberration calculations in lens design codes

On Feb 22, 11:28 am, Al Greynolds <awgreyno...@xxxxxxxxxxxxx> wrote:
On Feb 22, 8:59 am, Helpful person <rrl...@xxxxxxxxx> wrote:

I need to think about this.  However, 2nd order is a defocus term and
hence not part of the Seidel approximation.  Are not Seidels by
definition limited to spherical surfaces?- Hide quoted text -

Seidels are basically 4th order wavefront (3rd order ray)
aberrations.  Therefore, the contributions from a symmetric surface
(sphere or asphere) should include ALL 2nd and 4th order terms in the
series expansion of surface's sag.

Al

But the 2nd order is not an aberration.
.