Elements & Groups

A lens is one or more pieces of optical material (most commonly glass or plastic) designed to collect and focus all wavelengths of light at a single focal point to form a sharp image on the film.

When you look at the specifications of a camera you will notice that its lens is made of elements and groups.

The term element refers to the individual pieces of glass. The term group can refer to a single element, or two or more elements joined together. So a lens that has 5 elements in 4 groups has 5 pieces of glass with 2 joined together.

The use of multiple elements allows more optical aberrations to be corrected than is possible with a single element, but by itself the number of elements is no guarantee of quality.

Interesting note:
Up until the 1970s Minolta used a useful two letter suffix on the front of their lenses to designate the number of elements and groups. The first letter designated the number of groups: Q=4, P=5, H=6… The second letter designated the number of elements: D=4, E=5, F=6… From these letters we can tell from the PF on the lens of the Minolta AL for example, that it has 6 elements in 5 groups.