Superior quality across the to

EN: Superior quality across the to

Fotografie

To achieve a high level of sharpness both at the center and out to the edges of an image when shooting with a telephoto lens, it is desirable for the index of refraction of the front convex lens element to be as small as possible. Accordingly, the use of fluorite with its low index of refraction effectively improves image quality over the total image area.
Canon glossary EU