Tips to help you select the perfect light for your room. (Part 2)
Before you choose a light, you may want to know some basic terminology used in selecting and measuring light. Four terms or units of measurement of light are footcandles, candelas, lumens, and footlamberts.
FOOTCANDLES: Footcandles (fc) is the amount of light hitting a surface. Specifically, one footcandle equals the illumination produced by the source of one candle falling on one square foot of surface at a distance of one foot from the source of light. The amount of light (or fc) that a space should have depends on the task to be performed in the illuminated area and the age of the person using the space (as we age we typically need more light to perform certain tasks). For example a dining area may only require around 10-20 footcandles, while in the home office you may want 100 footcandles or more.
CANDELAS/ CANDLEPOWER: Candlepower describes how intense light output will be in a certain direction or at a specific point. Candlepower distribution curves are available from most lamp manufacturers and can help you determine how to ensure that the appropriate level of brightness is delivered in you room.
LUMENS: Lamps are typically rated by manufacturers in terms of lumens, or the amount of light output from that lamp. Lumens are also used to measure efficacy (the amount of lumens produced per watt of electricity consumed). One of the reasons many people switch from incandescent bulbs to fluorescent bulbs is because the fluorescent bulbs have a higher efficacy (they produce more light).
FOOTLAMBERTS: Much of the lighting in a space is actually contributed by light reflected from a surface. Footlamberts (fL) measure the amount of light reflected from a surface. If you want to get really technical, (fL= fc x % reflectance). For example, if 100fc reach a wall or table that is painted with a 40% reflective surface, then 40fL will reflect from that surface.