Originally Posted by Maris
When held together the powers cancel and the focal length is infinite. When separated, positive converging power (adjustable!) appears according to the distance between the lenses.
Excellent. I wondered what happened when they are separated. I knew that the method of adding dioptres I posted above was only for lenses next to each other or very close.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.