This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
The portion of a doublet lens located nearest the ground-glass. In most cases, when used without the front combination, it has a focal length almost double that of the complete lens combination and will produce an image practically double the size of that obtained by the complete lens.
Double-Concave, Concaval-Concave. A term applied to a lens thinner in the center than at the margin and having both sides hollowed out.
Double-Convex, Convexo-Convex. A term applied to a lens thicker in the center than at the margins, and having both sides extending outward in the form of a sphere.
An anastigmat lens having large aperture and great covering powers. Manufactured by Voigtlander.
A lens hollowed or depressed in the center.
Biconcave or Concaval-Concave. A lens in which both sides are hollow or concave.
A lens having one side hollowed out, the other being plane or flat.
A lens hollow on one side, the other being raised or convex.
A lens in which the various combinations may be arranged differently, or used separately, thus giving different focal lengths.
A lens the surface of which is in the shape of a sphere, the center being thicker than the margin.
A lens convex on one side and concave on the other.
A lens which is convex on both sides.
A lens convex on one side and plane on the other.
An anastigmat lens constructed of two lens combinations and a third single lens. Manufactured by Taylor, Taylor & Hobson.
A highly corrected anastigmat lens. Manufactured by Goerz.
A lens composed of two separate combinations.
The name applied to a highly corrected anastigmat lens. Manufactured by Voigtlander.