Signs of the Times - May 2020 - 24

LEDS + LIGHTING

Range of Sign Luminance
Candelas/
Square Meter

accuracy of this range by conducting
lab testing of new electric signs built
to conventional specifications. Additionally, the 2005 study High Efficacy
Signage conducted by Southern California Edison (in connection with its
research for the CEC) determined
the baseline luminance for the most
common type of internally illuminated
sign falls within the original IESNA/
IES range. ISA's sign-testing program
at UL's Allentown (PA) lab also confirmed a baseline luminance within
this same range.
Secondly, the scope of RP-39-19
mischaracterizes the functional
requirements for sign lighting.
The scope states, "Lighting should
maintain the minimum luminance
required for visibility." While this
statement might apply to outdoor
lighting devices, it's inappropriate
with respect to sign luminance.
Signs are messaging devices that
serve an entirely different function
than lighting fixtures. Whereas general
outdoor lighting is designed to illuminate specific areas to facilitate nighttime activities, signs are designed to
project their messages in all directions
from which the sign may be viewed.
Because electric signs are promotional

Candelas/
Square Foot

70-350

7-35

Lighted façades and fascia signs

250-500

25-50

Bright fascia sgns, as in shopping centers

450-700

45-70

"Low" brightness areas where signs
are isolated or have dark surrounds

700-1,000

70-100

Average commercial signs such as
for gas-station identification

1,000-1,400

100-140

High-rise signs and signs in areas
of concentrated sign competition

1,400-1,700

140-170

For emergency traffic control conditions
where communication is crtical

Published for decades in the IESNA/IES Lighting Handbook, this chart
describes the appropriate luminance range for internally illuminated signs.
devices for businesses, imposing
limits based on the "minimum luminance required for visibility" greatly
inhibits the core advertising function
of signage. That's true because the
luminance level at which a sign is
detectable (and legible) is far below
the level at which the sign is prominent.
Third, RP-39-19 adopts a "onestandard-fits-all" approach to
sign luminance. The RP-39-19 scope
states that it includes "on- and offpremise, internally and externally
illuminated, and electronic signs."
But key distinctions between these

Average Luminance (cd/m2)

2,000
1,800

1/8-in. Acrylic

1,600

3/16-in. Acrylic

1,400
Baseline

1,200
1,000
800
600
400
200
0

2

4

5

Number of Lamps

6

8

The center bars in this chart show baseline luminance values for lab-measured
signs incorporating two common face thicknesses (source: SCE High Efficacy
Signage Study, 2005).
24

SIGNS OF THE TIMES

MAY 2020

Potential Areas of Application

different types of illuminated signs
make this regulatory scheme inappropriate. For example, whereas
electronic signs typically incorporate
unshielded light sources (LEDs)
exposed directly to the human eye,
internally illuminated signs emit light
diffused and reduced in intensity via
transmittance through various plastic
face materials. There's simply no
rational basis for applying the same
luminance limits to all electric signs
regardless of type.
Historical data and modern testing
confirm that the sign industry
adheres to well-defined guidelines
governing the brightness of electric
signs and limiting escalation of sign
brightness over time. These guidelines have existed for decades and
they're essential to the proper functioning of electric-sign products under
a broad range of environmental
conditions.
Likewise, the unique nature, function
and variety of electric signs makes
the image of a "new sheriff in town"
packing a nit gun highly impractical as
a means of enforcement. Undoubtedly,
enforcing the RP-39-19 recommendations in this manner (or any other)
would severely impair the performance
properties of electric-sign products
coast to coast.



Signs of the Times - May 2020

Table of Contents for the Digital Edition of Signs of the Times - May 2020

Signs of the Times - May 2020 - Cover1
Signs of the Times - May 2020 - Cover1a
Signs of the Times - May 2020 - Cover1b
Signs of the Times - May 2020 - Cover2
Signs of the Times - May 2020 - 1
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