Photographic optics and colour photography [electronic resource] : including the camera, kinematograph, optical lantern, and the theory and practice of image formation (1909)
Johnson, G. Lindsay (George Lindsay), 1853-, Parsons, John Herbert, Sir, 1868-1957, donor, University College, London. Library Services · London : Ward & Co. · leaf 166
distances from the centre. The interval between these two planes is the measure of the longitudinal astigmatic interval. Let an assistant move a chessboard along the wall at the further end of a long room on a level with the lens, commencing from the axial line, and observe on the focussing-screen… … Fig. 103. flat, but curved, with the concavity towards the lens. This is termed " Curvature of Field." Hence definition falls off towards the edge of the plate. To improve the focus at I or d (Fig. 103), the screen must be pushed towards the lens. In practice we can mark off successive intervals of…
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