We have recently changed suppliers for some of our semi finished blanks and have been using Scopus lenses for our 1.5 index aspheric orders.
Now every time I run these the power comes out about +0.50 over using the sag they provide. The problem is consistent to the degree where if I reduce the sphere by 0.50 when computing or add 0.50 to the lap the lenses are fine.
I would like however to understand what is causing this problem.
I steer away from sagging the lens before computing as it is an aspheric but should there be a portion of the lens centrally which is spherical? I have sag guages 40 and 50 mm, would I be better of doing it this way?
The actual surface power printed on the box is stated for glass index, the lens is plastic but I assume this has nothing to do with the sag, or is there software out there that does it this way?
Any input would be appreciated,
Rick

PS we do not have problems of this type with any other blanks.