A dictionary of photography for the amateur and professional photographer (1889)
Wall, E. J. (Edward John), 1860-1928 · New York : E. & H.T. Anthony · leaf 161
r enamels, ivory, opal, or any textile fabric. Principal Axis is the right line which joins the centres of curvature of the spherical surfaces of a lens, or if one surface is plane, the principal axis passes through the centre of curvature of the spherical surface, and perpendicular to the plane… … secondary axis. The centres of curvature are the points from which the arcs of the circles forming the spherical surfaces of the lenses are calculated — that is, the centres of curvature are the centres of circles, of which circles the spherical surfaces of the lens are segments. Printing. This…
Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
