Hello,
I think I might have understood what makes some lenses swirl (like the petzval lenses).
It's probably a combination of over-corrected spherical abberation that should show up as ringed highlights behind the plane of focus and optical vignetting that is quite easily accomplished with a limiting hole in the back of the lens.
most of the lenses I have tested so far seem to have the ringed highlights in front of the plane of focus and that's not what I am after.
Are there any suggestions for lens designs which creates the ringed highlights behind the plane of focus?
Bookmarks