Photometric Data
Photometry is the science of measurement
of light.
Photometric data is a set of information
related to the amount of light emitted from
individual fixtures.
Independent labs are used to verify and
objectively report photometric data from
fixture manufactures
Photometric Data
Photometric Data may include the following
information:
Candle Power Distribution Curve
Luminaire Efficiency
Coefficient of Utilization
Spacing Criterion
Physical Dimensions
Lamp and Ballast Data
Efficacy
Photometric Data
Candle Power Distribution Curve
Describes the direction and the intensity of light
from the luminaire.
Candle power distribution curves can also help
determine if the fixture may create problems
with direct and reflected glare as well as
problems with hot spots.
Photometric Data
Candle Power Distribution Curve
‘Batwing’ Distribution (Good for Computers)
Photometric Data
Candle Power Distribution Curve
‘Even’ Distribution
Photometric Data
Candle Power Distribution Curve
Potential Problems:
Photometric Data
Indirect bat wing pattern
may reduce hot spots
(unacceptable bright
areas) on the ceiling.
Semi Indirect with a bat
wing pattern down to
reduce potential of
reflected glare.
Photometric Data
Luminaire Efficiency describes the amount of light that is
emitted from the luminaire compared to the amount of light
that is generated by the lamps.
All fixtures absorb some of the light from the lamps. Comparing
luminaire efficiencies between fixtures allow for quick energy efficiency
ratings.
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Photometric Data
Coefficient of Utilization (CU)
Coefficient of Utilization (CU) is the ratio of
lumens on the work surface to the lumens
emitted by the luminaire.
The CU is influenced by the reflectance values
of materials, size and shape of the room, and
the placement of the luminaire.
The CU is used in the lumen calculation method
that is used to determine the light levels for
ambient lighting systems.
Photometric Data
High Coefficient of Utilization (CU) values
means more light reached the work surface and
is more efficient.
Photometric Data
Coefficient of Utilization (CU) Table
pcc = reflectance value of the ceiling.
pw = reflectance value of walls
Typically the chart assumes a 20% reflectance value for the floor. (This is due
to typically dark colors and furnishings.)
Room
Ratios the
larger the
number the
larger the
room.
Photometric Data
Coefficient of Utilization (CU) Table
Note that small rooms with light colors have a high CU.
Large rooms that are dark have a low CU.
The CU represents the percentage of lumens that reach the work surface from
the fixture.
Photometric Data
Spacing Criteria describes the maximum acceptable
distance between fixtures when they are laid out in a room.
The number provided by the fixture manufacture is a ratio
that is multiplied by the distance between the work plane
that is to be illuminated and the bottom of the fixture.
Photometric Data
Spacing Criteria
If the distance between the fixture and the work plane is 6
then the maximum spacing criteria would be 6X1.2 = 7.2
parallel to the fixture and 6X1=6 90 degrees to the fixture.
(Remember that these are the maximum spacing
recommendations.)
7-2 MAX
6-0
MAX
Photometric Data
Physical Dimensions and Finishes
Photometric Data
Lamp and Ballast Data
Photometric Data
Manufacture Photometric Data
Fluorescent with Wrap Around Prismatic Lens
Fluorescent with Prismatic Lens
Deep Cell Parabolic Fluorescent
Semi Indirect Fluorescent
Indirect Fluorescent
Compact Fluorescent Down Light
Incandescent Down Light
MR 16 Down Light
HID Down Light
Photometric Data
Manufacture Photometric Data
HID Down Light
Pendent Fixture
Wall Washer
Placement Guide
Calculation Data