Lens Element
A single piece of shaped optical glass within a lens assembly.
Measured in
count
In depth
No single element can form a good image: each one introduces its own aberrations, and a lens design is essentially a set of elements chosen so their errors cancel. Modern zooms may contain twenty or more, which is why coatings matter so much — every additional air-to-glass surface is another opportunity for reflection and flare.
Examples in practice
A 24-70 mm f/2.8 zoom may list 21 elements in 15 groups, including three aspherical and four low-dispersion pieces.