FOOT-CANDLES: Light Intensity Required by Plants

Orchid Doctor

by Robert M. [Bert] Hamilton (Compiler)

Originally published in The Orchid Doctor in 1980 and 1988

Posted by Sys Admin almost 4 years ago.

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Cattleyas:2500-3500; dendrobiums: 1500-2500; miltonias: 800-1200; odontoglossums:800-1000; phalaenopsis: 800-1200. 0R81-112
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More The Orchid Doctor Articles under the Heading Foot-candles

Foot-candles Comments
FOOT-CANDLES: Conversion Table Using a Weston light metre and a sheet of white matte cardboard, take exposure readings and rate them with foot-candles of light 16(6400), 15(3200), 14(1600), 13(800), 12(400), 11(200) etc. down to 4(1.6); the average for orchids is 14(1600); bright daylight with overhead sun is 10,000fc (England). OR-22 0
FOOT-CANDLES: Fc Rating Meaning One foot-candle equals the light emitted by one candle one foot away; expressed ratings are measured at noon Standard Time on a clear day; the maximum amount would be recorded around June 21 and the minimum December 21 in North America; a June 21 reading of 3950 fc. means a range of 2000 0 4000 for the year. A85-332 0
FOOT-CANDLES: Interpretation of the Meaning The recommended foot-candles of light for a species means the direct or incident light. A64-975 0
FOOT-CANDLES: Meaning The amount of light emitted by a burning candle one foot away; 500fc. is about enough to read a newspaper; a clear day in June (in Maine) would be 12,000. A86-814 0
FOOT-CANDLES: Minimum Amount Required to Affect Flowering This has not been determined; it is generally assumed that more than two fc. of light intensity is required to delay flower initiation by orchids; most commercial growers use lOfc. or more. A67-45 0
FOOT-CANDLES: Optimums For cattleyas the range is 2400 to 3600, for phalaenopsis it is 1500 to 1800. A86-815 0
FOOT-CANDLES: Outdoors, in Alberta During the summer there are about ll,000fc.; during winter between 4,500 and 6,000fc. A60-770 0
FOOT-CANDLES READING: By Means of Photographic Light Meter (weston Master) Read the light reflected from the surface of white blotting or type-writing paper without light from any other source; multiply the meter reading by four. A67-415; A74-34; Sekonic meter. A68-431 0
FOOT-CANDLES READING: Gro-lux Fluorescent Tubes Multiply foot-candles by 2.18 for correct fc. reading under Gro-Lux when using photo-exposure meter readings under normal light. OD70-242 0
FOOT-CANDLES READING: Using a Built-in Light Meter in a Camera Set the speed dial at ASA25 and the shutter speed at 1/60; aim camera at center of sheet of paper eight inches by eleven, eight inches distant; the lens opening (f-stop) is adjusted until the meter shows correct exposure; if lens opening is f/2 illumination is about 40fc.; f2.8 is 75fc.; f/4 is 150fc.; f5/6 is 300fc; f/8 is 600fc; f/11 is l,200fc.; f/16 is 2,400fc.; all figures approximate. A78-408 0
FOOT-CANDLES READING: Using Exposure Meter Set ASA at 10 and exposure at 1/100 second; hold the meter pointing at the center of clean white surface as closely as the smallest diameter of the surface(such as paper) casting no shadow and read: f/3.5 is 400fc.; f/4 is 500fc.; f/4.5 is 650fc; f/5 is 800fc; f/5.6 is l,000fc; f6.3 is l,300fc.; f/7 is l,600fc.; f/8 is 2,000fc; f/9 is 2,400; f/11 is 4,000fc. ; f/12.7 is 5,200fc; f/16 is 6,400fc. A62-105+; A69-1003; A75-680 0
FOOT-CANDLES READING: Using Photographic Equipment Use the meter on the camera; point latter at center of sizeable white surface without casting a shadow; set ASA at 10.3 and the shutter at 1/100 second and read: f/3.4 is 400fc.; f/4 is 500fc.; f4.5 is 650fc.; f/5 is 800fc f/5.6 l,OOOfc.; f/6.3 is l,300fc. ; f/8 is 2,000 fc; f/10 is 3,200fc; f/11 is 4,000fc; fl2.7 is 5,200fc; f/16 is 6,400fc; A65-244; A74-896; OR76-360 0
FOOT-CANDLES READING: With Photographic Light Meter Meters can be bought for reading foot-candles; with a Weston photographic meter convert to fc. by measuring light reflected from a piece of white matte paper and multiply the light value by four. A73-1081 0
FOOT-CANDLES: Requirements A sodium vapor lamp illuminated all night 100ft. away from cymbidiums in a greenhouse may not affect their flowering because they are temperature-responders; but plants requiring short days will not flower. A86-815 0
FOOT-CANDLES: Requirements for Main Types Cattleyas/laelias 3,000-3,500; cymbidiums 3,000; dendrobiums 3,000-3,500; odontoglossums 2,000+; oncidiums 2,500+; paphiopedilums 800-1,300; phalaenopsis 1,500-2,000; vandas and allied 3,500-4,000. OR76-360In summer: cattleyas 2,400-3,600; cymbidiums full sun; phalaenopsis 1,200-1,500; in winter: no shade generally for cattleyas and cymbidiums; if winters are partly sunny some shade is required by phalaenopsis and paphiopedilums. A61-734; OD73-198 0
FOOT-CANDLES: Requirements for Some Types Epidendrums like 3,600, and some will stand full sun; laelias like 2,400 to 3,600. A61-982 0

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