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Specifi cations, compliances and dimensions subject to change without notice
EATON Halo Product Catalog Recessed Downlighting
19
Lighting Effects
Halo Recessed Lighting
Point-to-Point Calculations
The calculation of foot-candles at a point, no matter if it is on a horizontal, vertical
or tilted surface, can be accomplished with the inverse square law. The law states
that the illuminance is proportional to the candlepower of the source in the given
direction and inversely proportional to the square of the distance from the source.
In addition, as a surface is tilted away from the source, illuminance will decrease
in a ratio equal to the cosine of the angle of incidence.
The inverse square law formula can be expressed in various ways; the two most
useful follow. Version 1 is ideal for the complexities of three-dimensional space as
no trigonometry (cosine) is needed, just the simple X, Y and Z coordinates of the
layout. It is also very useful in calculating foot-candles from the CBCP of accent
lights. Version 2 is useful for calculations that can be laid out in two dimensions
and when it is easy to find the cosine of the aiming angle. Insert your data into
either easy-to-use formula to calculate the initial foot-candle level at a point.
Lighting throughout an area which
produces general illumination. The
appropriate Halo recessed fixtures are
available to provide patterns of light
distribution for this purpose. These
units direct light in specific patterns
to illuminate areas without drawing
attention to the fixtures themselves.
Ambient Lighting
Lighting directed to a specific area
to perform a specific task. Use Halo
fixtures with narrower beam patterns and
high illumination levels. Task-Ambient
Lighting–The combination of task and
ambient lighting should provide a level
of ambient lighting that is lower than
the task yet is designed so the ambient
complements the task lighting. Here
luminance ratio should be considered.
Luminance ratio is the measure of task
or accent to surrounding ambient lighting.
For example, retail stores may use 5-to-1
task-to-ambient lighting on cash registers
for transactions and 10-to-1 accent-to-
ambient lighting on displays to draw
maximum attention to the products.
Task Lighting
Lighting of vertical surfaces defines
form, space and texture. It can visually
increase the apparent size of a room
while improving visual comfort. Halo has
skillfully engineered fixtures designed to
direct a spread of illumination on these
surfaces. Halo fixtures may be selected
based on the size of the space, the level
of illumination and intensity desired,
energy efficiency and controllability.
Wall Washing
Directional lighting used to focus
attention on a particular object or
surface. Its intensity levels vary
according to ambient illumination
levels. Higher ambient levels require
higher accent illumination to provide
the necessary contrast (luminance
ratio). This requires adjustable fixtures
which can deliver higher illumination
levels and precise beam distributions.
Halo adjustable trims are often used in
accent lighting and offer the range of
intensities and beam spreads necessary
for controlled quality lighting.
Accent Lighting
COS TAN
0˚ 1.0 .000
5˚ .996 .087
10˚ .985 .176
15˚ .966 .268
20˚ .940 .364
25˚ .906 .466
30˚ .866 .577
35˚ .819 .700
40˚ .766 .889
45˚ .707 1.0
X
D
Y
To find distance D:
D = X
2
+ Y
2
or D =
Y
cos
To find aiming angle :
TAN =
X
or
COS =
Y
YD
Version 2
FC
=
I x cos
Where: I
= CD towards Point
D
2
D
= Distance to Point (square root of X
2
+ Y
2
)
= Angle between incident light ray and normal to the surface
Horizontal
X
X
FC FC
DDY Y
Vertical
Version 1
FC
=
I x N
Where: I
= CD towards Point
D
3
D
= Distance to Point (square root of X
2
+ Y
2
+ Z
2
)
N
= Distance Normal to the Surface
X
(N)
(N)
Y
DZ
FC
FC
Y
X
ZD