2. The innermost layer is the
retina –the light-sensing
portion of the eye. The
retina has retentive value
which means that it stores
images for a fraction of a
second It contains rod
cells, which are
responsible for vision in
low light, and cone cells,
which are responsible for
color vision and detail.
3. The color-responsive chemicals in the
cones are called cone pigments and
are very similar to the chemicals in the
rods.. There are three kinds of color-
sensitive pigments:
•Red-sensitive pigment
•Green-sensitive pigment
•Blue-sensitive pigment
•Each cone cell has one of these
pigments so that it is sensitive to that
color. The human eye can sense
almost any gradation of color when
red, green and blue are mixed.
•The eye can process about 100
shades of gray. Movie film can handle
about 50 and video about seven
4. If you divide a still image into a
collection of small colored dots,
your brain will reassemble the dots
into a meaningful image
If you divide a moving scene into a
sequence of still pictures and show
the still images in rapid succession,
the brain will reassemble the still
images into a single movie (It takes
about 15 to 20 frames a second
before you begin to see smooth
animation) This is based on the
retention capability of the eye.
5. A single cluster of LEDs is used as a pixel.
A pixel is a picture element; the smallest individual
unit or piece of a video display image. A pixel is
an individual dot in a video display.
Each pixel has its own color and brightness
attributes.
6.
7. A display’s pitch is its measurement of distance
from the center of one pixel to the center of
another pixel.
The pitch determines the viewing distance. The
smaller the pitch, the shorter the viewing distance.
8. Minimum Distance: The point at which the fully illuminated red,
green, and blue components appear to the eye to blend into
white.
Maximum Distance: The point at which the smallest characters
the display can generate begin to be illegible. This point varies
greatly with the content of the display.
Minimum distance = 2’ x pitch
◦ Ex: 2’ x 12 mm = 24’
Maximum distance = min. distance X 7
◦ Ex: 24’ x 7 = 168’
OR
Maximum distance = 30 to 40 times the height of the display
◦ Ex: 9’ x 12’ = 270’ – 360’
9.
10.
11. Fill factor refers to the amount of black space
between pixels.
A high fill factor means more LEDs per ft² and
generally a smoother looking picture.
Low Fill Factor High Fill Factor
12. Resolution is the total
number of pixels in a
display.
The higher the number of
pixels the greater the
possible detail.
A standard video signal
(NTSC) has a native
resolution of 645 x 485
pixels.
300x300
80 x 80
13. Relationship in a video image between the
width of the image and the height of the image
expressed in generic terms of units width by
height (4:3, 16:9).
The aspect ratio for NTSC video and most
computer monitors is 4:3. The standard aspect
ratio for digital HDTV is 16:9.
14. LED brightness is measured in
candelas per square meter
(cd/m2) a.k.a. nits (roughly 0.3
foot lamberts). The higher the
number, the brighter the display.
No correlation with illuminated
brightness such as LUX (Lumens
per m²).
1500 nits provides readable text
in outdoor daylight. Video
requires up to 5,000 for good
color depth.
Indoor video requires 1,500 to
2,500 nits.
Barco brightness measured at
6500ºK.
15. Measured in degrees Kelvin,
color temperature is an
indication of the amount of
“warmth” (yellow, red tones)
or “coolness” (blue tones) in
a white light.
Standard video color
temperature is 6500ºK.
Barco’s color temperature is
adjustable.
16. Contrast ratio is a measure of the dynamic range of a displayed
image - the distance between the “whitest” white and the
“blackest” black in a video wave form.
There is no industry standard method of measuring contrast
ratio. LED has high numbers because it has no residual glow
when turned off in a dark room.
A more important number for video is shades of gray.
17.
18. International IP scale is a unique reference base for all types of
industrial applications.
Tiles resistant to:
◦ Water
◦ Heat
◦ UV
◦ Vibrations
◦ Dust
◦ Salt
◦ Animal intrusion
19. Typical LED voltage drop is 2 to 3 volts
per 25 feet of LED strips. Most LED
products will start to dim when voltage
is lowered more than 2 volts.
20. Lumens measure how much light you are getting
from a bulb. More lumens means it's a brighter
light; fewer lumens means it's a dimmer light.
Lumens are to light what pounds are to bananas
gallons are to milk
Lumens let you buy the amount of light you want.
So when buying your new bulbs, think lumens, not
watts.
The brightness, or lumen levels, of the lights in
your home may vary widely.
21. In short, the NIT is a measurement of direct
light while a lumen is a measurement of
reflected light.
It takes 3.5 lumens per square meter is equal to
1 nit per square meter. So 7000 lumens equals
2500 nits. One 100 light bulb is 1600 hundred
lumens or 457 nits.
RELIABILITY is critical for Daylight displays -
Prime time sports events, live shows, corporate vents, paid advertising in prominent locations do not mix well with product failures. Failures are highly visible.
Therefore take ALL Precautions to optimize RELIABILITY
WATER and DUST/POLUTION resistance are 2 keys aspects that can improve reliability
IP Chart defines how resistant to dust and water a product is. EVER product should have an IP certification. Even a rating of IP00 still tells you how you need to protect it.
Heat resistance is another key area. However, many LED walls require air conditioning not just because of the requirement to cool the displays but because humidity must be removed.
Where a wall is NOT waterproof considerable care needs to be taken to ensure that no humidity can get onto the circuit boards. This needs something far more than a simple shelter.
Before you place a $1M+ non-waterproof LED wall outside consider how much protection you need to take to avoid circuit board failures.
