I have searched everywhere on the internet, and could not find anything.
I give up.
Gee my first time here.
I have no idea what fresnel types are by name, but I currently work with two. One is a fresnel front with the lamp side of the lens flat and the other has the lamp side. in a con cave stlye--not refering to a steped lens, though that could be considered a third. I have the Fuchs book so maybe I can research it if I remember.
There is the possibility that the flat back sides either hava a pattern or are clear.
I did some quick research.
T. Fuchs book predates fresnel lenses in Theatre. The W. Bellman book (mid 70's) noted cheap lenses and expenseive lenees, cast lenses and ground lens with the step lens a variation of the fresnel. If there is something else then it is beyound simple research and will make us all feel stupi d
By my counts, we have all four of them mentioned now. Anyone wish to sum up the four types and explain the differences between them?