Originally Posted by nemesis
,it must be flat and not convex like a prescription lens for specs,otherwise it won't work.
Why? Would it not be a converging lens?
I'm casting mind back to the optics module in A level physics now so bear with me. It can't be flat on both surfaces or it's a plain sheet not a lens.
My specs lenses are convex on the front and concave on the back, but thicker at the outer edge than in the middle. This makes them diverging lenses, to correct short sight. They don't magnify, they reduce.
A diopte of 0.0656 would mean converging. Diverging lenses have negative numbers.