a question need your help

[seanl]

no , what i know is Rodenstock PAL for individual but not finished products.

[AWTECH]

PAL back surface difference

If the design is good meaning that the lens is designed for the surface to be on the back of the lens, then the optics can be equal to the non-spherical surface being on the front. There is very little reason to consider back side PALs unless they are being generated on an individual basis, since there is not spherical surfacing equipment that can easily change the front sphere to accomodate the various powers. Making individually cast progressives as finished product sounds like an inventory nightmare.

What is the reason for your question? Is there a product you know of that has this back side PAL?

[seanl]

if the PAL work surface is the back surface, what the differen effect shoud be or is there any difference exist? when we produce these PAL, what we should note and what problems can come out?