Handbook for Sound Engineers

1580 Chapter 44

• High contrast is shown as blacks and whites with
  very little gray.


• In digital technologies, contrast is the difference
  between the luminance or brightness of an ON pixel
  and an OFF pixel.

Contrast is used as a marketing specification and is
the most misstated of all specifications from manufac-
turers. The proper method to measure contrast is by
using a sixteen zone black and white ANSI test pattern
and comparing the average of the dark rectangles to the
white rectangles to get the proper contrast ratio. As a
point of reference, when measured in this manner, the
most expensive digital cinema projectors in the world
will produce approximately 500:1 contrast and a typical
boardroom projector will produce less that 100:1
contrast in a typical lighting condition.

44.2 Display Color

Each display technology produces the color we see in a
different manner but they all utilize the primary colors
of red, green, and blue as well as the secondary colors
of cyan, magenta, and yellow to create the full color
spectrum we see onscreen.
Going back to our physics class in high school, we
remember that white light, when viewed through a
prism, produces a veritable rainbow of colors, known as
the full color or electromagnetic spectrum. The easiest
way to remember the visible color spectrum is the name
ROY G BIV (red, orange, yellow, green, blue, indigo,
and violet).
Infrared and ultraviolet light are not visible, and fall
at the far extremes of the spectrum.
In the world of professional audiovisual, you may
encounter what is known as the CIE chromaticity
diagram (color chart). This chart illustrates the full color
spectrum, including wavelengths of light measured in
nanometers and color temperature, measured in degrees
Kelvin. As a specific point of reference, you can see the
overlap of red, green, and blue, producing white light.
In modern display technologies, color is created in a
variety of ways, by the manipulation of white light:

• Color is produced from the light of a projector lamp
  shining through a color wheel, in the case of single
  chip DLP (digital light processing).


• Color is produced from the light of a projector lamp
  shining through a transmissive display device, or
  bouncing off a reflective display device, such as
  LCD, three chip DLP, or LCOS (liquid crystal on
  silicon).
  
  
  • Color is produced from an emissive (light producing)
    display device, such as a CRT, plasma display, or
    OLED.
  
  
  • Color is produced from the backlight of a transmis-
    sive display device, such as a flat panel LCD.
  
  
  
  

Color and color space can be calibrated in the

majority of displays by using instruments known as

colorimeters. These devices measure the visible color

spectrum and permit the technician to calibrate for a

specific color temperature depending on the application.

Most displays are set for 6500 Kelvin, also known as

D65, which replicates an image in a full daylight mode.

44.3 Display Resolution

The resolution of digital display technologies is fixed as

in the reference to fixed matrix displays. Resolution

relates directly to visual acuity and what the eye can

see. Each display technology differs in the spaces

between the pixels and this is called the fill factor. The

displays with the highest fill factor appear to have less

of what is known as the screen door effect thereby pro-

viding a look closer to that of an analog image of

35 mm color film or CRT displays. The higher the num-

ber of pixels, the more detail in an image.

• In digital displays, resolution is the number of pixels
  (picture elements or individual points of color)
  contained on a display, expressed in terms of the
  number of pixels on the horizontal axis and the
  number of pixels on the vertical axis—e.g.,
  1920 × 1080.


• The sharpness of the image on a display depends on
  the resolution and the size of the display. The same
  pixel resolution will be sharper on a smaller display
  and gradually lose sharpness on larger display
  because the same number of pixels is being spread
  out over a larger number of inches.


• In terms of fill factor, LCD has the most space
  between pixels, with DLP providing more fill factor,
  and LCoS providing the highest fill factor available
  today.

44.4 Display Scanning

Television signals and compatible displays are typically

interlaced, and computer signals and compatible dis-

plays are typically progressive (noninterlaced). These

two formats are incompatible with each other; one

would need to be converted to the other before any

common processing could be done.