What is HORIZONTAL DISTRIBUTION?
Owing to the shape of filaments the greatest part of light from most filament lamps is given sideways (perpendicular to the filament).
The light will have different intensities (candlepower) in different horizontal directions.
The average of intensities from all horizontal directions is called the MEAN HORIZONTAL CANDLEPOWER of the bulb.
When referring to the candlepower of an incandescent lamp, the MEAN HORIZONTAL CANDLEPOWER is meant, unless otherwise specified.
references for this page: HORIZONTAL DISTRIBUTION, MHC, MEAN HORIZONTAL CANDLEPOWER