Anyhow, about that purple halo business, correcting a fast achro for e line, it seems like a much more usable thing to do than correcting it for d line and let 430nm go too wild.
I once started a thread about having a fast achro design that was designed ONLY to be used at low powers...the idea being your out of focus color blurs would be a bit smaller on the ends of the spectrum...while the range of colors that where typically diffraction limited you would let blow up a bit.
Did not seem to generate much interest and I'm not skilled enough to investigate the idea myself.
And now I'm thinking of some risque VHS tapes containing "Wavelengths Gone Wild" episodes...
Edited by starcanoe, 12 January 2021 - 10:42 AM.