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Specifi cations, compliances and dimensions subject to change without notice
EATON Halo Product Catalog Recessed Downlighting
18
Lighting Properties
Halo Recessed Lighting
Lamp Shielding
Angle
Lamp
Cutoff
Lamp Image
Shielding Angle
Lamp Image
Cutoff
Cutoff & Shielding Angle
The lamp cutoff angle of a luminaire is the angle between the vertical axis (nadir)
and the first line of sight when the bare source is no longer visible. Lamp image
cutoff is measured the same way as lamp cutoff, but it occurs when the image of
the lamp is no longer visible in the reflector. The shielding angle is the compliment
of the cutoff angle.
When both the lamp cutoff and lamp image cutoff are equal, the optical system
has no spill light and uses all of the light in the useful beam. Equal cutoff to
lamp and lamp image also provide higher visual comfort for the space.
Luminaire Effi ciency
Luminaire efficiency is the ratio of lumens emitted by a luminaire in relation to
lumens produced initially by the lamp contained within. It includes both the optical
and thermal characteristics of the luminaire and is measured under controlled
ambient conditions of 77°F (25°C). Luminaire efficiency does not indicate any
information on the direction of the light leaving the fixture or its visual appearance.
Units: Percentage %
Illuminating Engineering Society (IES)
Evaluating Light Source Color Rendition
Illuminating Engineering Society (IES) TM-30-15 method for evaluating light source
color rendition. IES TM-30-15 is a technical memorandum published by the IES
that details a new method for evaluation and identification of color rendition
properties of a light source. The IES notes that no single measure can accurately
identify all aspects of the color rendition of light. Therefore the TM-30-15 Technical
Memorandum describes a method for evaluating color rendition of a light source
based upon quantifying the fidelity (closeness to a reference color illuminate)
through a Fidelity Index (Rf) and gamut (increase or decrease in chroma or saturation
relative to a reference color illuminate) through a Gamut Index (Rg) of a light
source. The method also generates a color vector graphic that indicates average
hue and chroma shifts, which visually plots values of Rf and Rg, and aids with
interpreting the method’s results. TM-30-15 method provides equations and direction
for calculating Rf and Rg, including the spectral reflectance functions for 99 Color
Evaluation Samples (CES). A software tool is included with TM-30-15 as provided
to aid in calculation and display of the results.
Efficiency is a comparison of like terms; in the case of a lighting fixture, lumens from
the luminaire vs. from the lamp. This measure of efficiency is concerned with the
amount of light a luminaire can provide given the specific light source it employs.
Effi cacy
Efficacy is the ratio of the luminous flux (lumens) produced by a source in relation
to the energy (watts) it consumes. While efficiency is a comparison of like terms,
efficacy is a comparison of unlike terms –- the lumen and the watt. It is analogous
to the miles per gallon rating of automobiles. It compares how a light source
converts power into light. For example:
13.5W LED Luminaire (LED, Driver, Optic/Trim)
1100 lm/13.5W = 81 LPW (Total Luminaire Efficacy)
26W CFL lamp
1800 lm/28W = 64.2 LPW (Bare Lamp Efficacy)
26W CFL Luminaire (Lamp, Ballast, Trim)
with 70% Luminaire (Trim) Efficiency
1260 lm/28W = 45 LPW
Units: Lumens per watt (LPW or lm/W)
Candela Diagrams
(Candle Power Distribution)
Candela diagrams provide an illustration of the intensity and distribution of light.
This allows quick estimates on how useful a particular fixture would be in an
application. Polar graphs provide a visual indication on how narrow or wide a
beam a fixture produces. Two sets of angles are referenced, vertical and horizontal
angles. Vertical angles range from 0° at nadir to 90° along the ceiling line. The
number of horizontal angles referenced depends on the rotational shape and
symmetry of the light distribution. Sections, or planes of data, are cut at various
intervals to describe the intensity changes at the same elevation angles. The
0°-180° plane slices the luminaire along the axis of the lamp, the 90°-270° plane
cuts across the lamp axis. Additional planes are supplied every 22.5° where the
light distribution becomes more asymmetric. In general, numerical data instead of
small polar diagrams should be used for calculations, since the diagrams become
difficult to read at the higher elevation angles and at angles surrounding the fixture.
Units: Percentage % Symbol: p
Spread
Reflection
Diffuse
Reflection
Specular
Reflection
Reflectance is the ratio of luminous flux (lumens) reflected from a surface in relation
to luminous flux (lumens) incident onto the surface. Types of surface reflectance
range from the specular to the diffuse (lambertian), with many objects exhibiting
combinations. Typically, reflectance becomes more specular with larger incident
angles. Reflectances of room surfaces are important consideration when calculating
illuminances using the "Lumen Method."
Refl ectance
Reflectance % =
Reflected Lumens
Incident Lumens
LED LPW =
Delivered Luminaire Lumens
Luminaire Watts
CFL, Halogen LPW =
Lamp Lumens X Luminaire Efficiency
Luminaire Watts
Efficiency % =
Luminaire Lumens
Lamp Lumens
IES Method for Color Rendition
Color Fidelity Color Gamut Graphics
The accurate rendition of
color so that they appear as
they would under familiar
(reference) illuminates
The average level of
saturation relative to familiar
(reference) illuminates
Visual description of hue
and saturation changes.
Color Vector Graphic
Gamut Index (R
g
)
60-140 when Rf > 60
Fidelity Index (R
f
)
scale up to 100
(0-100)
or
Vector
Gra
lR
Field Angle: 50% maximum
candlepower.
Beam Angle: 10% Lamp beam spread to
maximum candlepower.
Center Beam
Candle Power (CBCP):
Maximum candlepower of lamp at nadir.
Nadir
50% of
Maximum
Candlepower
180º
0º
270º90º
10% of Maximum
Candlepower