Lighting Control Options: Diffusing Panels

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Lighting diffusers are a good option for controlling the quantity and quality of light in exhibit cases and from overhead light sources.

What are light diffusers?

Diffusers are rigid panels that redirect light. A diffusing panel inserted between the light source and the viewing area is a practical way to reduce the amount of light by 18 to 50%. Diffusing panels also soften and even out the appearance of hot spots from lamps. There are two types of diffusers: louvers and textured panels.

• Louvers: The simplest louvers, often referred to as "eggcrate" due to their appearance, are made up of a series of straight-sided squares of approximately .5 inches. Parabolic louvers have more complex profiles to the grid; these angled or curved surfaces are often coated with a reflecting material. Light is directed as it passes through the louver, and the total amount of light reaching the viewing surface can be decreased with proper selection. Micro- louver panels use fine embedded louvers to control light scattering. Louvers can block light from reaching sensitive objects located in close proximity.
• Textured or tinted panels: A variety of textured or tinted plastic and glass panels are commercially available. The textured and semi-opaque qualities of the panels cut the total amount of light transmission by up to 50%. Panels are typically pebbled, frosted or hazed, or constructed with internal ribbing similar to a corrugation. Textured panels can be purchased in colored, transparent plastic, and tinted or clear glass. The tinted products can lower the light transmission even more than the clear textured products. The quality of light may be affected by the tinted products.

How do I install diffusing panels?

Choice of the diffuser panel appropriate for your application can be guided by product literature and manufacturer representatives or a lighting designer. Louvers and textured panels are available in acrylic, polystyrene and/or polycarbonate plastic; louvers are also made from aluminum and textured panels from glass. Any of these materials are safe for use near collection objects.

Case lighting is a common application for diffusing panels. The diffuser is usually located just above or below the solid panel separating the display and lighting chambers. The separating panel is usually glass or a rigid plastic, and may itself serve as a diffusing panel if textured, sand blasted, or milky material is used. The panel needs to be well-sealed with gaskets and fasteners or the use of a caulking material. Plastic diffusion panels are subject to warping and/or melting if located too close to lamps. Otherwise, diffusers should last indefinitely.

Diffusers can also be installed as ceiling panels to affect overhead lighting or can be located in front of track lighting.

Products, Manufacturers, and Suppliers

Mention of a product, manufacturer, or supplier by name in this publication is for information only and does not constitute an endorsement of that product or supplier by the National Park Service. Listed materials have been used successfully in past applications. It is suggested that readers also seek alternate product and vendor information to assess the full range of available supplies and equipment.

Louvers, Acrylic Eggcrate, Parabolic and Plastic Diffusers Panels

• A.L.P. Lighting and Ceiling Products, Inc

Tinted and Textured Plastic Panels

• Lexan® Polycarbonate Products
• Plexiglas Acrylic Sheet Rohm and Haas