0 used to refer to a lens (= curved piece of glass) that you can look through and see things clearly that are at various different distances:
I can't get used to my new varifocal glasses.
Some camera lenses are varifocal to give an improved performance.
Frames are designed for a wide range of prescriptions, including bifocal and varifocal lenses.
An interesting issue is the extent to which bifocal and varifocal spectacles might be a contributory factor in falls on stairs.
Samyang is known for producing varifocal and monofocal lenses, autoiris and fixed iris lenses, interchangeable lenses that are compatible with the cameras produced by other companies.
