First, information about aspheric lenses is presented. This is followed by a study that was done on the durability of various metals used to make pinholes. The result is an image that is not as sharp as it would otherwise be. Spherical aberration is worst in fast optical systems, that is, where the diameter or aperture is large relative to the focal length. Hence, aspherics are effectively utilized in such systems.
Aspheric lenses are available in a wide range of diameters and focal lengths.
Lenses as small as 1 to 2 mm diameter and focal length are used as laser diode collimators. At the other extreme, aspherics as a large as 16 inches in diameter are being used in holography.