This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 edition. Excerpt: ...which the lamp throws on the paper can be calculated from the distance of the lamp, and consequently we can read on the instrument the brightness of the object to be measured. Fig. 49. Photometer to Measure Relative Brightness. In Figs. 50 and 51 are shown two landscapes which were photographed and at ...
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 edition. Excerpt: ...which the lamp throws on the paper can be calculated from the distance of the lamp, and consequently we can read on the instrument the brightness of the object to be measured. Fig. 49. Photometer to Measure Relative Brightness. In Figs. 50 and 51 are shown two landscapes which were photographed and at the same time were measured with the photometer, and it will be seen that the sky in these has a brightness of about 1500 foot-candles, while the deepest shadows in the foreground have a brightness of about 60 foot-candles. It is often believed by photographers that the range of light intensities occurring in natural objects is very great, and that in an ordinary landscape, for instance, the sky will be enormously brighter than the shadows, but this idea is quite incorrect. In a bright landscape with heavy shadows, the sky is only about 30 times as bright as the deepest shadows, while in the case of open landscapes in which there are no close objects in the foreground, the range of intensities will be much less than this, the sky often being only 5 or 6 times as bright as the shadows. The range of light intensities, therefore, with which it is necessary to deal in ordinary photography will vary from, perhaps, 1 to 4 at the least up to 1 to 50 as a maximum, and the brightest part of a landscape--the sky--will have a brightness of from 1000 to 3000 foot-candles. This is the photometric brightness of the sky itself; but when we take a photograph, we are concerned not with the brightness outside but with that inside the camera; that is, with the brightness of the image which falls upon the film. This brightness depends upon the aperture of the lens, and we can calculate it from the fact that at an aperture of.f.8 the photometric bright ness of...
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PLEASE NOTE, WE DO NOT SHIP TO DENMARK. New Book. Shipped from UK in 4 to 14 days. Established seller since 2000. Please note we cannot offer an expedited shipping service from the UK.
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PLEASE NOTE, WE DO NOT SHIP TO DENMARK. New Book. Shipped from UK in 4 to 14 days. Established seller since 2000. Please note we cannot offer an expedited shipping service from the UK.
