A negative or divergent meniscus lens is also convex-concave, but is thinner at the center than at the edges.

Positive achromatic lenses.
These lenses are considerably reduced values of spherical aberration, coma and chromatic aberration. Best used to replace single components where performance must be improved.

Negative achromatic lenses.
Typically used to reduce spherical aberration, coma and chromatic aberration

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