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.

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

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.

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.

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.

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’

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

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

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.

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.

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.

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.

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

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.

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 bananasgallons are to milkLumens 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.

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.

Typical under eave lighting methods

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