Basic Lighting Terms
by
Ronald Lazarus

• Wattage is a measurement of energy not light and that is why you don’t use a toaster to read.
• Lumen is the measurement of light at the light source (light bulb*). Not where you read.
• Foot candle (FC) is the measurement of light on a surface (1 foot candle=10.76 Lux). This is the the light that you see.
• Photometry is the measurement of light on any surface.
• Uniformity is the relationship between maximum and minimum light on a surface.
• Contrast is the relationship between print or an object to its immediate background.
• Glare is excessive light that is reflected back to the eye creating discomfort.
• Color rendering index (CRI) is the measurement of how natural and vibrant colors look. The (real world) lowest is 20 and the best 100.
• Kelvin or correlated color temperature (CCT) is the actual color appearance of light. The range (in the real world) is from a low of 2,000k (warm light) to a high of 7,500k (cool light). Warning; daylight or full spectrum lighting (over 5000k features blue light) which is suspect in retinal damage for people over 55 and/or with macular degeneration, on some medications, who are diabetic or have blue eyes.
• Nanometer (NM) used as a unit of wavelength measurement.
• Light bulb life when 50% of a large group of light bulbs are still working (called lamp life).
• Ambient light is the general lighting in an area.
• Task lighting is lighting that is used for a specific visual task.
• Transformer is a magnetic or electronic device used to start and run some light bulbs.
• High intensity discharge light bulbs (HID) mercury vapor, metal halide and high pressure sodium light bulbs (for commercial use). Light bulbs in which an arc passing between two electrodes in a pressurized tube causes metallics to vaporize and produce large amounts of light.
• Fluorescent light bulbs are a low pressure mercury vapor discharge light source that creates ultra- violet energy which is converted into visible light (available from warm to cool light).
• Incandescent, the most common (regular light bulb), involves electricity passes through a wire (usually tungsten) that causes the wire to glow inside a vacuum or gas filled light bulb. It is safe for the eyes and provides good color (CRI) and warm light.
• Halogen (short for Quartz Halogen) light bulbs are incandescents that use halogen gas and a quartz glass bulb to provide a brighter whiter light with better color (CRI) and increased lamp life.

*In the professional world of lighting a light bulb is called a lamp.

Please research your lighting options. You only have one set of eyes!!