Glossary of Terms

Ampere - Also known as 'amps.' Refers to the amount of electric current flowing through a circuit, and is used to calculate the wattage of a lamp.

Aperture - Aperture, in optics, the maximum diameter of a light beam that can pass through an optical system. The size of an aperture is limited by the size of the mount holding the optical component, or the size of the diaphragm placed in the bundle of light rays. The hole in the mount or diaphragm that limits the size of the aperture is called an aperture stop. Thus, an aperture stop determines the amount of light that traverses an optical system and hence determines the image illumination.


Accent Lighting  - Additional lighting–often from directional light sources–used to highlight particular areas or objects. Commonly used in retail displays and galleries.


Appliction  - Also called “lighting application”, it refers to the particular use the lamp is being put to. (e.g. high-bay industrial application or retail lighting application.) The term can also refer in a general way to “application engineering” which deals with specific parameters and usage of light sources. (e.g. how to do a lighting layout, where to place fixtures and so on.)


Ballast  - A device used with an electric-discharge lamp to obtain the necessary circuit conditions (voltage, current and waveform) for starting and operation. All fluorescent and HID light sources require a ballast for proper operation. Dimming ballasts are special ballasts which, when used together with a dimmer, will vary the light output of a lamp.


Candela  - The current SI unit of luminous intensity. One candela is equivalent to 1 lumen/steradian. Used to express both Beam Intensity (Beam Candela) and Mean Spherical Intensity (Mean Spherical Candela). Also referred to as Candlepower (cp).


Candlepower  - Old definition of luminous intensity. One candlepower (cp) was the luminous intensity of a standard candle made of whale wax, weighing 1/6 lb, 7/8 in. in diameter, and burning 120 grains per hour. The current SI unit for luminous intensity is the candela (cd). One candela (cd) is the same as one candlepower thus a source with a luminous intensity of 10 candelas could be referred to as a 10 candlepower source.


Color temperature - Is measured in Kelvin and indicates whether a lamp has a warm, midrange or cool color appearance. Warm light sources, such as incandescent lamps, have a low color temperature (2000-3000K) and feature more light in the red/orange/yellow range. Cool light sources, such as some HID or fluorescent lamps, have a high color temperature (>5000K) and feature more light in the blue range.


Diffuser - A cover or case over a light source designed to soften (or diffuse) the light it emits. Apollo MFG produces a series of colorful, themed fluorescent light covers called DesignScapes that can help curb the brightness of your fixture, all while adding scenery to your space!


Diffuser - Whether or not the lamp lumens can be varied while maintaining reliability.


Direct lighting - Lighting that casts all, or at least 90%, of its light downward. The term can also refer to the distribution of light or the fixtures that produce this type of lighting. With intense beams, direct lighting is very dramatic, rendering forms and textures well. Typical fixtures include recessed lights, track lights, some pendant lights and task lights.


Gobo  - A “Gobo” is a small, stenciled circular or square disc, and used in lighting fixtures to create a projected image or pattern. The term is an acronym for “Go Between Optics”, describing the location where it needs to be positioned in the light path of a lighting fixture. Apollo MFG has thousands of standard patterns to choose from!


Keystoning  - A process by which unwanted distortion of a gobo pattern is corrected, and is typically required when the projection angle exceeds 30 degrees. Learn more about our keystoning services!


Lumens  - A unit of luminous flux. This measurement expresses the overall light output or quantity of light produced.