Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'' (1912)
Barrows, William Edward, 1878-1960 · New York ; London : McGraw-Hill Book Co. · leaf 186
ods of obtain-ing the amount of light available for illuminating purposes wemay now proceed with the several methods of performing illu-mination calculations. It is the common practice in thiscountry to consider the intensity of illumination on a horizontalplane as the basis of comparison or… … Fig. 99.—Illumination calculations by the point-by-point method. the floor. In offices and similar interiors the plane would bethat of the desk top or about 30 in. from the floor. The Point-by-point Method.—One of the first methods ofdetermining the value and distribution of illumination is knownas…
Light · Photometry · Electric lighting
Internet Archive · Boston Public Library · Public Domain Mark 1.0. Free to use for anything.
