Photographic optics and colour photography : including the camera, kinematograph, optical lantern, and the theory and practice of image formation / by George Lindsay Johnson.

  • Johnson, G. Lindsay (George Lindsay), 1853-1943.
Date:
1909
Catalogue details

Licence: In copyright

Credit: Photographic optics and colour photography : including the camera, kinematograph, optical lantern, and the theory and practice of image formation / by George Lindsay Johnson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    The positions of the lenses are marked in the above figure, which will guide the amateur in putting them back, if removed for cleaning. The Portrait Anastigmat, Planar, and Unar lenses of Zeiss and Eoss, the Cooke lens, Dallmeyer's Portrait Stigmatic, and Busch's Anachromat, Beck's Unofocal and No. 2 Extra Rapid Rectilinear are suitable for this purpose, and give superb images. Dallmeyer & Co. make a special projection lens of very flat field (Fig 179). Beck has lately introduced a multifex objective, which, by simple separation of the lenses in a draw tube, will produce any focus from 6 in. to 20 in. Perkeu & Son have also introduced a similar lens on the telephoto principle. The definition of the image depends far more on the perfection Fig. 179.—Dallmeyer's Lantern Lens. of the lens than on the condenser, although bubbles in the latter are apt to show on the screen, which they will not do in the lens. The Screen.—The best form of screen is undoubtedly a whitewashed or distemper - coloured wall. For ordinary sitting, 20 ft. long, one 6 ft. square is ample. For a room 30 ft., an 8-ft. screen is best. For a room 50 ft. long, a 10-ft. screen is about right, and so in proportion. In private houses it is a good plan to have the screen made of stiff twill or linen, and rendered quite opaque with two coats of white paint, to which a trace of black or blue may be added, sufficient to slightly tone down the glare of the white. Ordinary cotton sheeting lets too much light through. If, however, it be thoroughly