Lighting

The following page describes a the general characteristics to keep in mind when dealing with lighing.

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Terminology

Candela (cd)

SI (International System of Units) base unit of luminous intensity that measures power emitted by a light source in a particular direction. The flame of a single candle emits light with a luminous intensity of approximately one candela.

Efficacy

Refers to the measure of efficiency a particular lamp converts electrical power (measured in watts) to light (measured in lumens) without regards to the effectiveness of the illumination.

Footcandle (fc)

a US unit of measure* of light intensity that measures the actual amount of light falling on a particular surface. One footcandle is equal to one lumen per square foot.
*Note that this unit of measurement is a non-SI unit

Lumen

The SI unit of Luminous Flux

Lux (lx)

The lux is an SI derived unit of measurement used to describe light intensity.

Glare

A source of light that is above the observers current state of adaption. The average human eye is capable of adapting to a wide range of light intensities, but not if two different intensities are present at the same time. An example would be standing directly under a street light in the middle of a dark parking lot with no other lights on. The observer would be able to see perfectly well directly under the light (given enough time for that person's eyes to adapt). However, that person would not be able to see well into the dark areas around the street light. Glare is occasionally confused as being the reflection off of a surface such as glass, water or some other surface.

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Lamp Types

There are many different types of lamps used in architectural lighting, each with it's own characteristics. The following is a list of commonly used lamp types, along with a brief description. You can find more about a specific lamp type by going to its wiki page.

Light Emitting Diode

Metal Halide

Neon

Sodium Vapor

Sodium vapor lamps fall into two categories, high pressure and low pressure.

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Measure of Light