San Diego Plastics
2220 McKinley Avenue
National City  CA  91950
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  Parabolic Principle / Definitions

Parabolic louvers represent the most sophisticated and optically precise lighting control media available for fluorescent lighting fixtures and lighted ceilings. The parabola is the basis of a parabolic concept. The properties of a parabolic louver are its ability to redirect a ray of light downward out of the 60 to 90 visual discomfort zone.

The parabolic louver has four primary functions. First, to hide the lamps. Second, to control the light into a designated area. Third, to reduce glare and fourth, to give a pleasant, low brightness appearance. The basis for lighting performance and control of a parabolic louver is the shape of the vertical cell walls. These are parabolic surfaces that act as small reflectors directing all light into a task area (0 to 45 zone) where it can be utilized most effectively. The absence of light above a 45 high viewing angle, eliminates objectionable source brightness or glare, thus providing great visual comfort. The measurement of the direct glare (from the media surface) is termed Visual Comfort Probability, or V.C.P. and is rated in a percentage from 0% (poor) to 100% (excellent). Most parabolic louvers provide a V.C.P. index of 90% or over for most room sizes. A simple explanation of V.C.P. ... if 100 people were in a room viewing a fixture with a louver from the same location in the room and 90 of the 100 found the appearance visually pleasant, that would represent a V.C.P. of 90%. It must be remembered that visual comfort is as important to a lighting system as the amount of the distribution of the light. With a V.C.P. rating of 90% and above, it is possible to function more effectively with less light ... an important factor when dealing with energy consumption considerations. The illustration indicates how a parabolic louver controls and directs light into the 0 - 45 zone. All illumination above 45 strikes the parabolic wedges and is redirected at an angle equal to or less than the shielding angle. This principle of light control prevents any apparent brightness from normal viewing angles. The parabolic design concept for louvers eliminates unwanted glare or brightness from a lamp source and creates a comfortable zone utilizing the directed light. A lens, although it diffuses the lamp source, can cause uncomfortable brightness and glare ... much like the brightness from a candle. The parabolic louver redirects light into specific zones, much like a flashlight. The light is directed where it is needed. Each parabolic louver has distinct angles, V.C.P.'s and efficiencies. This catalog showcases A.L.P. products.

Care & Handling

Great care should be exercised when handling parabolic louvers, avoiding contact with oily and/or foreign substances. Always handle louver panels with clean gloves - never use bare hands. Always install these louvers when the space is ready for occupancy - never during construction. The care and maintenance of lighting fixtures and panels require professional and regularly scheduled maintenance. We strongly recommend the use of a local lighting maintenance company.

Surfaces & Finishes

Parabolic louvers are available in specular and semi-specular finishes. Each of these surface variations will render a somewhat differing light distribution, intensity and source brightness. In general, the darker the louver color the less efficient the lighting output with a marginal improvement of the V.C.P. rating. The basic design concept of parabolic louvers is to provide for a superior V.C.P. rating by contour design and not darker colors. The color selection is one of aesthetics, not improved visual comfort (V.C.P.).

Specular finished parabolic louvers provide the most precise lighting and brightness control. These louvers direct all light to the task area (0-45) and usually generate V.C.P. ratings of 95%+ for most room sizes.


Parabola is the basis of a parabolic louver. The inherent property of a parabola is its ability to redirect a ray of light downward out of the 60 to 90 visual discomfort zone. Parabolic louvers using this principle directs the light downward into the 0 to 45 zone.
V.C.P. or Visual Comfort Probability is a projected visual comfort level of direct glare from a media surface rated in a percentage of 100 people in a room, ranging from 0% (poor) to 100% (excellent).
Efficiency is the amount of light emitted from a fixture versus the total light from the source within the fixture.
Shielding Angle/0 To 45 Zone is the horizontal angle at which the lamp is obscured. Within the shielding angles is the 0 to 45 comfort zone. The depth and cell size determine the exact shielding angle, (i.e. 1/2" x 1/2" x 1/2" is a 45 shielding angle).


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