Lens materials
Abbe number
Optical glossaryLens materials
A measure of how much a material disperses light into colors. It falls as index rises; lower Abbe can mean faint color fringing at the edges of strong lenses.
- 1.50: Abbe number 58
- 1.60: Abbe number 41–42
- 1.67: Abbe number 31–32
- 1.74: Abbe number 32–33
From CLIFF's index data · Abbe by lens material
In more depth
The Abbe number compares how strongly a material bends light overall with how differently it bends the colors within it. A high number means the colors stay together; a low number means blue is bent noticeably more than red, and the colors separate slightly at the edge of a strong lens.
You look through a lens's center most of the time, where the effect is negligible. It shows when looking obliquely through a strong prescription, as faint color fringes on high-contrast edges. The size of the fringe grows with the lens power and with how far off-center you look, and shrinks as the Abbe number rises.
Across the CLIFF index range
| Index | Material | Abbe |
|---|---|---|
| 1.50 | CR-39 | 58 |
| 1.56 | — | — |
| 1.60 | MR-8 | 41–42 |
| 1.67 | MR-7 / MR-10 | 31–32 |
| 1.74 | MR-174 | 32–33 |
Curve depth is relative to a 1.50 lens of the same power, and reflection is for one bare, uncoated surface — both calculated from the index itself. Material and Abbe number are the material manufacturers' published figures, not CLIFF measurements.