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| glossary of terms |  |
What is INITIAL LUMENS?
light output of a bulb is usually expressed either in units of lumens, or, candlepower (CP).
light output of miniature bulbs is often expressed in candlepower, but, larger bulbs are usually expressed in lumens.
One lumen is equal to the amount of light emitted by one candle that falls on one square foot of surface located one foot away from one candle.
A uniform source of one candlepower placed in a sphere emits 12.57 lumens or mean spherical candela (MSCP) equals 12.57 lumens; meaning that 1 candle has a total output of light (light output in all directions) equalling 12.57 lumens.
A 100 watt common incandescent bulb emits around 1700 lumens.
Lumen rating of a light bulb is a measurement of ALL the light output from that light bulb from all directions.
light output diminishes over the life of the bulb.
Initial Lumens is the lumens rating for a brand new light bulb.
Design Lumens is the rated lumens measured at 40 percent of the bulbs rated life.
For general lighting, bulbs usually need to be replaced when their lumens output drop to around 50% of the Initial Lumens.
halogen bulbs are designed to hold their lumens output very well over their life.
references for this page: LUMEN, DESIGN LUMENS, EFFICACY, INITIAL LUMENS, LPW, LIGHT ENERGY, LIGHT OUTPUT, LIGHT, LUMENS OUTPUT PER WATT, LUMENS, POWER FACTOR
references to this page: /BL, /BUG-YELLOW, /FS, /GR, /HO, /IR, /OT, /SB, ARC TUBE, BALLAST, BALLAST FACTOR, BREAKDOWN VOLTAGE, CANDLEPOWER, COEFFICIENT OF UTILIZATION, COLOR RENDERING INDEX, COLOR SPECTRUM, COLOR TEMPERATURE, CONVERSION TABLE, COSINE LAW, COVE LIGHTING, DARK-EFFECT, DESIGN END FOOT CANDLES, DICHROIC MIRROR, DIFFUSION, DISCHARGE LAMP, DOWN LIGHTING, ELECTRIC DISCHARGE LAMP, ELECTRONIC BALLAST, ELLIPTICAL REFLECTOR, EXITANCE, FIELD ANGLE, FILAMENT, FLUORESCENT LAMP, FLUX, FOOTCANDLE, GENERAL LIGHTING, GLASS, HALOGEN BULB, HIGH OUTPUT FLUORESCENT, HIGH PRESSURE SODIUM, HORIZONTAL DISTRIBUTION, HOURS, ILLUMINANCE, ILLUMINATION, INCANDESCENT BULB, INDIRECT LIGHTING, INITIAL MAXIMUM BEAM CANDLEPOWER, INTENSITY, LAW OF INVERSE SQUARES, LENS, LIGHT BULBS, LIGHT CENTER LENGTH, LOUVER, LOW PRESSURE SODIUM, LUMENS PER WATT, LUMEN DEPRECIATION, LUMEN MAINTENANCE, LUMINANCE, LUX, MEAN SPHERICAL CANDLEPOWER, MERCURY VAPOR LAMP, METAL HALIDE LAMP, NEODYMIUM, PAR LAMP, PHOSPHOR, PHOTOMETER, PHOTOMETRY, PHOTON, PREHEAT, RAPID START, REFRACTION, REFRACTOR, SCOTOPIC VISION, ULTRAVIOLET, VISIBLE SPECTRUM, VOLT, WAVELENGTH