Originally Posted by
packfanrlb
The traditional method was to cross them 90 apart.If you wanted to make a +2.00-8.00,you'd put a +2.00/+6.00 on the front and a -8.00/-4.00 on the back side.As explained to me by an old master at B&L,during WWII when metal for laps was scarce,labs would use two identical laps,one convex and one concave and by changing the opposing axes,you'd pic up a new power every12.5 degrees.Now with no concave laps or plus cyl. semi finished lenses the art of cross cylinders appears to have died.
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