Platinotype : its preparation and manipulation (1895)
Abney, William de Wiveleslie, Sir, 1843-1920, Clark, Lyonel · London : Sampson Low, Marston & Co. · leaf 150
se the plane side of the condenser is away from the light. A photographic lens of some seven and a half inches focus, and which has a fairly flat field, is then, without any stop being inserted, held in a perfectly rigid camera front, or in a clamp, and so placed that the focus of the rays, coming… … Fig. 4. is of the required size on a board, S, to which a sheet of white paper has been pinned. It frequently happens that a circle of orange and blue light is seen cutting the picture, this shows that the adjustments are not accurate. If the coloured circle cuts the corners of the picture…
Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
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