Cutoff Classifications

Luminaire classification for
controlling stray light

 

Full Cutoff    Cutoff    Semi-Cutoff
(rollover a selection above)

 
Luminaire Classifications for Controlling Glare

The Illuminating Engineering Society of North America (IESNA, or IES) provides classifications for luminaires according to their glare control and high-angle brightness. These classifications include full cutoff, cutoff, semi-cutoff and noncutoff.

Lithonia Lighting uses Nighttime Friendly to identify products that reduce negative impacts on the nighttime environment. Products designated with the Nighttime Friendly logo have no uplight, meet the IESNA definition for full cutoff optics and reduce high-angle brightness.These measures of luminaire performance are consistent with sustainability standards for light pollution reduction.

For applications where there is a concern with light trespass on neighboring properties, consider products that limit light behind the pole such as the Type 4 sharp cutoff optical system or house side shielding.

 

 
Classification Definition Benefits Limitations
Full Cutoff

Zero intensity at or above horizontal (90 above nadir) and limited to a value not exceeding 10% of lamp lumens at or above 80.

Limits spill light onto adjacent property, reduces glare. No light is emitted directly from the
luminaire into the sky.

May reduce pole spacing to maintain uniformity
and increase pole and luminaire quantities.
Cutoff Intensity at or above 90 (horizontal) no more
than 2.5% of lamp lumens, and no more than 10% of lamp lumens at or above 80.
Small increase in high-angle light allows increased pole spacing. May allow some uplight from luminaire. Typically a small overall impact on sky glow.
Semi-Cutoff Intensity at or above 90 (horizontal) no more
than 5% of lamp lumens and no more than 20% at or above 80.
High-angle light accents taller vertical surfaces
such as buildings. Most light is still directed
downward.
Little control of light at property line. Potential for
increased glare when using high wattage luminaires. Typically directs more light into the sky than cutoff.
Non-cutoff No limitations on light distribution at any angle. Uniform luminous surfaces such as internally illuminated signs or globes. Wattage should be limited. Suitable for sports lighting, facade, landscape or other applications where luminaires are tilted due
to limitations in pole or fixture locations.
Location and aiming are critical. Most likely of all
categories to produce offensive brightness and
sky glow.