Originally posted by house The optical diagram looks identical to the dfa100 but as you mention they claim to have added special glass!
Bdery what's your view on that?
I don't think anyone can draw actual conclusions based on drawings shown on a public website. I know *I* would never agree to have the details of my own private and complex designs available for all my competitors to see. Those drawings are instructive but not to be taken as fully accurate.
The Tokina has a much wider diameter, for the record, maybe that's just how they built it, maybe that's for a reason.
Originally posted by house it sounds unlikely that they used aspherics and "super ed" in that first version?
Aspherics, absolutely. It's been around for, what, a hundred years?
"Super ED" is just a label. Controlling dispersion has also been of interest for optical designers for quite some time.
Again, you cannot just swap components in a design. If you replace an element by another which does different things with the light paths, then the whole design needs to be revised. Sometimes effects are minimal, sometimes not.
See it this way. If element 3 on the optical path outputs light in a different way, then element 4 isn't getting it where expected, and can't direct it where it should. So element 4 needs to be adapted too, and so on and so forth.