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Lenses and Louvers

Controling the Light Beam with Lenses and Louvers

Author: Steve Parrott

The following descriptions and photometric renderings* illustrate how supplemental lenses change MR-16 light beams. Four parameters of the beam are changed: Beam spread Beam edge definition/diffusion Overall beam diffusion Brightness	Rendering of a 35W, 36 degree, MR-16 CAST Bullet mounted 18" from a wall, tilted to a 3 degree angle.
Optical Spread Lens (COSL) This glass lens sports ridges in a cross-hatched pattern. It's effect is called prismatic diffusion. It widens the beam slightly, softens the edges and softens the hot spot at the center of the beam. It cuts center beam brightness by about 20%. It's typically used when lighting walls or plant material when a softer, less defined beam is desired.	Addition of COSL, Optical Spread Lens. Note that beam is wider, edges are slightly more soft.
Optical Frosted Spread Lens (COFL) This glass lens is etched to create an even diffusion. Its effect is similar to the COSL but the diffusion effect is more pronounced, creating a wider beam with very diffuse edges and nearly obscuring the beam's hot spot. It reduces the center beam brightness by about 46%. This lens can be used whenever a highly diffuse light source is needed, especially useful when lighting certain plant material or statuary where hot spots would be problematic.	Addition of COFL, Optical Frosted Spread Lens. Note that extreme diffusion towards beam edges makes edges less visible.
Honeycomb Louver (CXL1) This black anodized aluminum louver is composed of a honeycomb pattern of dividers. It cuts out stray light (glare) past about 45ß from the beam center. It also hardens the beam edge slightly and accentuates the hot spot. It decreases center beam brightness by about 30%. It's main use is in controlling glare. Typical scenarios would be to shield glare from fixtures in plant beds that are near walkways or driveways; or in cases where light might otherwise spill into windows.	Addition of CXL1, Honeycomb Louver. Note that beam spread is very similar to 'no lens' but edges are sharper.
Optical Linear Spread Lens (COLL) This glass lens sports linear ridges. Its effects are the same as the COSL with the exception that it significantly narrows the beam in one direction creating a narrow oval. It decreases center beam brightness by about 50%. This lens is used whenever a long narrow diffuse beam is desired. Typical uses are for uplighting trees or flagpoles, as a wall wash for low retaining walls and for lighting along paths or driveways.	Addition of COLL, Optical Linear Spread Lens. Note extreme widening of beam and retention of fairly hard edges. Since the beam shape is oblong, the above rendering shows the widest part of the beam illuminating the wall.
	This is the beam resulting from turning the lamp so the narrow edge of the beam contacts the wall. Note, you would never light a wall in this fashion.
*These photometric renderings were generated by AGI-32 using accurate IES files. The files were obtained by actual measurements of the MR-16 lamp with filters in place. Renderings from these files are especially accurate because our light intensity measurements are accurate to one-hundreth of a candela, compared to usual IES files rounded to whole candelas.

(Document No. 00050: Created on: 07/12/08 Last modified on: 08/25/09)