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TECHNICAL INFORMATION
Truck-Lite Full Line Product Catalog
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307
TEC
There are many different methods for measuring light. One of the most accurate tests for measuring the intensity
of light within the pattern a lamp produces is known as an Iso-Candela Scan. The illustration below is an actual
Iso-Candela scan from a lamp engineered by
Truck-Lite
®
. There are points of intense light in red; these are often
referred to as “hot spots.” We can also see areas of green which are areas of mid-range light which transitions out
to areas of blue which are areas of very little light. These colors are simply representational of the light intensity in
that area, they have nothing to do with the actual color of the lamp’s light.
Iso-Candela scans are rendered by placing a highly-calibrated tool, known as a Photo-Detector Cell, into a light
tunnel along with a light source. The Photo Detector Cell acts as an eye looking at the light source, and is able to
transpose the light beams it “sees” into the colorful chart you see below.
This specific scan shows a head-on angle of a lamp. We can look at the key at the bottom of the image to gauge
the candela value for that specific area. Red being the hottest or area with the most intense light, reveals the area is
around 16,000 candela; dark blue being the coolest or areas with the least amount of light, reveals areas around 25
candela.
This scan shows the distribution of light as if you were looking directly at it. Some scans show a bird’s eye view,
which allow the viewer to see the width and length of light distribution, while others examine light distribution of a
lamp from a different angle, i.e., 45°.
Notice the hot-spot on this scan. This lamp is designed for distance, so the hot-spot is very pronounced. To
achieve distance from a lamp one must concentrate the light into a specific area, this concentration creates a hot-
spot. This lamp measured all the way up to 20,000 candela!
In summary, let’s review:
• Wattage is a measure of power consumed by a lamp, not the light emitted by it
• Lumen value can only be accurately calculated using an integrated sphere, and that there is a difference
between
Cold Lumen Values
and
Warm Lumen Values
• Candela is a measure of light intensity, not total light output
• Iso-Candela Scans measure light intensity and pattern
Light pattern, lumen value, and candela value all play very important roles in LED lighting. Though it may be
tempting to trust a single number on a page, you are now prepared to make a more informed, rounded decision
when choosing your next lamp.
The Iso-Candela Scan:
Putting It All Together