The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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light by means of a prism constructed of the glass, and measur-ing the refraction of a certain line of the spectrum by suitable instruments. The different coloured rays of the spectrum have different refractive indices, that for violet being the greatest, and that for red the least; and this fact is taken into consideration in the achromatising of lenses. (For further information on Reflection and Refraction the reader is referred to any elementary work upon light or optics.)
Table of Indices of Refraction (for D).
Registration. Any photograph may be registered at Stationers' Hall on payment of a very small fee, and if the registration is effected by the actual producer of the photograph, before any copy has been sold, the copyright is secured. A photographer cannot secure copyright in a photograph which he makes as a matter of business for a customer, and copyright only extends to the photograph, never to the original. Let us suppose a photographer to have access to a unique document, picture, or even photograph. For illustration, let us assume it to be the first daguerreotype ever produced. He could secure copyright in his reproduction, but any other photographer