Incorrect Seidel aberration calculations in lens design codes

ZEMAX at top of its Seidel table says the results are good only for
symmetric spherical and conic systems but it DOES take into account
4th order term on an even asphere. On the other hand it DOES NOT take
into account the contribution of the 2nd order even asphere term to
the Seidels (athough it does properly use this term in the paraxial
ray trace).

LENSFORGE (a Mac code) includes the contributions of both the 2nd and
4th order even asphere terms to the Seidels, but in general doesn't
calculate the Seidels correctly for systems with mirrors!

Even though aberration coefficients have lost a lot of their utility
with today's ability to trace thousands of real rays per second, I
find it surprising that ANY modern lens design code should have
problems with the relatively simple calculation of Seidel aberrations.

Al Greynolds
www.ruda.com
.