Illuminating Engineering Society, Association of Public Lighting Engineers (Great Britain) · [London] · leaf 254
<x>Ox4jr lumen 6 per THE ILLUMINATING ENGINEER (may) 239 ■cent, of the light is directed on the ceiling,and that 75 per cent, of this is reflecteddownwards, the brightness of the ceilingshould be :— 5000 x 4tt 75 75 1200 Xl00Xl00=176 foot-candle8. to be lighted, I would like to point outthat… … A Drawing Office lighted by indirect arcs. If the ceiling is treated as an infiniteilluminated planethe calculated illumination (176 ft.-candles) agrees quite closelywith that actually measured. If we regard the ceiling as an infiniteilluminated plane the illumination in the•centre of the room…
Lighting
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