Content is Power
Barco LiveDots
Content is Power
How does content on LED
displays affects your OPEX?
Author
Bas van Heek
Product Marketing Manager
bas.vanheek@barco.com
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INTRODUCTION
In this white paper we discuss the effect of different content on
power consumption of LED displays. We will explain how colors
are generated and what impact this has on power.
Additionally, we will link this to contrast (or brightness), as
both are closely related. The best displays in the market are
the ones that find the best balance between both, and those
that allow you to manage that relationship correctly.
Our goal is to increase the understanding when reading and
comparing specifications in today’s over-saturated world of
LED display systems. We want to provide knowledge that will
help decision makers to make the right decisions and
influencers specify the right product.
We hope that after reading this white paper you will better
understand how content and brightness work and what their
impact is on your application.
LED DISPLAY PRINCIPLES An LED display uses an array of light-emitting diodes (LED) as
a video display. By default, LED display technology is a light
emitting technology. Independent of which type of LED is used
– SMD1 or TH LEDs – light is radiated from each individual
LED. For both technologies, each individual color R-G-B is
controlled separately to create basically any color within the
RGB color spectrum.
Fig. 1: RGB color spectrum (source: Wikipedia – RGB color model)
1
SMD (Surface Mounted Device) and TH (Thru-Hole or discrete) LEDs are both
type of LEDs used in display arrays. For TH each R-G-B dies are individually
packed, whereas for SMD R-G-B dies are combined into one package. Both
SMD and TH refer to the way the LEDs are fixed to the PCB.
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LEDs within the display array are grouped by at least one Red
(R), Green (G) and Blue (B) LED, all together at full intensity
creating white. At zero intensity, the LEDs emit no light at all
and the display is black (or the color of the surface, hence all
98% of all LED display have a black front surface). This group
of LEDs is often referred to as ‘pixel’.
Fig. 2: Color creation on LED displays (source: Wikipedia – RGB color model)
CREATING COLORS
To create any color within the RGB color spectrum, the
intensity of each LED must be controlled. Most LED displays
nowadays specify a color depth of 16bit/color. This means for
each LED R-G-B there are 216 or 65,536 steps between zero
and full intensity, basically controlled by the LED driver that
manages the current over the LED die. In total this can
theoretically generate 216 x 216 x 216 or 281 trillion colors per
pixel. Theoretically, as also dimming has an impact on color
reproducibility.
In the following example we simplify how a color is generated.
We take a random color within the spectrum, purple. We use a
computer to generate purple on an 8 bit/color scale with color
intensities between 0 and 255.
Fig. 3: Random color creation using 8bit/color on windows PC
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This color purple is generated by
146/256 x Red
57.03% Red
39/256 x Green
15.23% Green
130/256 x Blue
50.78% Blue
Percentages are relative to full intensity.
COLOR VS POWER
To convert this into power consumption we first need to
address a bit about power consumption of a typical LED
display. We consider here 1m² of a typical LED display system.
A typical LED display system consists of LED modules2,
controller, power supply and a heat management system.
All components consume power, even when brightness of the
LED display is zero (color = black).
Blue
Green
Red
General
Fig. 4: Power consumption per color and total for 1sqm LED display (source: Barco)
In Fig. 4 power consumption per color on 1sqm of a typical
LED display is displayed. In the table, the following power
consumptions are shown, assuming maximum intensity:
General (BLACK)
Full RED
Full GREEN
Full BLUE
Full WHITE
74W
74 +
74 +
74 +
74 +
116
146
126
116
=
=
=
+
190W
220W
200W
146 + 126 = 460W
In summary it becomes clear not every color contributes
equally to the total. This is caused by different power required
for each color LED to function on one hand, and calibration
(contribution per color to create perfect white D65) on the
other hand.
2
PCB with LEDs mounted to the front, some intelligence and connectors on the
back, often packed within a plastic housing optionally foreseen with protective
potting or coating against water ingress
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If we take same assumptions (maximum intensity) to create
purple as randomly selected above on this particular display
type, power consumption will look like:
Purple
0
50
100
150
200
250
Fig. 5: Power consumption of typical LED display showing purple (source: Barco)
The above figure can be summarized as follows:
PURPLE:
74 + 66(R) + 22(G) + 64(B) = 226W
Assuming the display show purple over its entire surface (the
average color is purple), the average color purple consumes
226/460 = 49.1% of white.
CAMPAIGN EXAMPLE
Based on this theory, let’s discuss two Apple campaigns and
what the impact is on power consumption and cost.
Fig. 6: Reference advertisement 'Black'
Fig. 7: Reference advertisement 'white'
We are using http://mkweb.bcgsc.ca/color_summarizer/?analyze , a free
online tool to determine the average color of both images. The
gives the following results:
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Table 1: RGB color analyser results
Image
Black
White
R
32
232
G
27
228
B
26
226
RGB
32.27
232
We now convert this into power on our typical LED display.
Black:
74 + 32/256 x 116 + 27/256 x 146 + 26/256 x 126 = 117W
White:
74 + 232/256 x 116 + 228/256 x 146 + 226/256 x 126 = 420W
Considering pictures in Fig. 6 and Fig. 7 the average power
consumption per square meter is 117W for the ‘black’ image
and 420W for the ‘white’ image. A difference of 303W, or in
other words – the ‘black’ image consumes 72.1% less power
than the ‘white’ image.
COST IMPACT
Assuming this would be a billboard campaign on 60sqm US
billboards, we can calculate the annual power cost for both
reference images.
Table 2: Power consumption and cost
Image
Power/billboard
Black
White
W
7,020
25,200
Power/
billboard/year
kWh
61,495
220,752
$/kWh
0.14
0.14
$
8,609
30,905
Power cost, similar as power consumption is 72.1% lower on
‘black’ image compared to ‘white’ image.
The above example still assumes full brightness 24/7 and full
year of operation. In real-life the display will only operate 18/7
and follow a daily brightness cycle, so difference should be
corrected for that. Nevertheless, the difference remains 72.1%
although yearly costs will be less.
BRIGHTNESS VS POWER
Talking about brightness, best not to underestimate the power
of brightness either. There are a couple of reasons why
managing the brightness correctly directly impacts your
business case.
1. Brightness has direct impact on power consumption
which affects your OPEX
2. Brightness has direct impact on LED lifetime, and thus
operational lifetime of your investment
3. Correct brightness has impact on general acceptance of
LED displays in urban areas
a. Impacts driver safety
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b. Impact acceptance of people living in direct
neighborhood
c. Impacts likelihood of getting building permits for
outdoor digital advertising displays
4. Last but not least, correctly managed brightness control
contributes positively to your company’s CSR score.
Brightness is generally managed and controlled by a display
agent using local light sensor readings of the environmental
lighting conditions to set the correct display brightness. This
automated process can be completed by additional rules to
ensure correct brightness.
For the following calculations we assume the following settings.
We will again use the ‘white’ example picture from Fig. 7.

Automated brightness control
enabled

Maximum brightness setting
75% of max

Brightness during calculated night-time
3%

Display Off
midnight to 6am
For the sake of argument we neglect in this example
brightness variations due to different lighting conditions during
the day, we assume during daytime the display is directly set
to maximum allowed brightness according to predefined rules
above. The brightness cycle of the display will look as follows:
90
80
70
60
50
40
30
20
10
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Average brightness in this case is:
(6x0 + 7x3 + 11x75) / 24 = 35%
In the example of the ‘white’ example picture from Fig. 7 this
will result in:
74 + (232/256 x 116 + 228/256 x 146 + 226/256 x 126) x 0.35 = 195W
An average power consumption of 195W instead of 420W, a
saving of 225W, or 53.5%. Since we are taking into account
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optimal brightness settings here, this does not affect your
picture quality at all. On the contrary, it improves the image
quality. Image quality is optimal while color reproduction,
brightness and contrast are in balance. Not were brightness is
maximum.
Fig. 8: Schematic view of key to perfect image quality
Converting into cost again, using same example of standard
60m² US Billboard will result in the following savings:
Table 3: Power consumption and cost 100% vs 35% average brightness
Image
Power/billboard
White
(100%)
White
W
25,200
Power/
billboard/year
kWh
220,752
$/kWh
0.14
$
30,905
11,700
102,492
0.14
14,348
(35%)
A simple feature as brightness control can provide cost savings
up to 53.5%, or 276$/m²/year in this example.
In real-life this will even be lower, since brightness curve
during day will gradually increase to maximum and gradually
decrease to night-time settings again, depending on how fast
light conditions are changing.
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CONCLUSION
Since LED display technology is light emitting technology, and
colors are generated by changing intensity of individual light
sources (LEDs), color has enormous effect on power
consumption and therefore operational expenses.
Depending on colors and backgrounds used in advertisement
on LED displays, power cost can be reduced by numbers up to
75%.
At the same time, predominantly dark content will also
contribute to the lifetime of the display, which also impacts
return on investment.
Secondly, managed brightness control also contributes to
power consumption and operational costs, apart from some
other important but less direct cost impacting arguments. With
managed brightness control significant cost savings up to 55%
and more can be achieved.
Again, this not only contributes to operational costs, it also
stretches the lifetime of the display further improving return
on investment.
Barco LiveDots
President Kennedypark 35
B-8500 Kortrijk
Belgium
+32 5636 8869
sales.livedots@barco.com
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