Color Perception and Your TV

Capturing Color

  • First, you have to “capture” the image. A video camera has to see the light reflecting off objects and coming through a lens. The entering light consists of all the colors reflected off the target object(s).
    That light enters the lens and hits a chip (in the old days, before chips, the light had to pass through a specially built vacuum tube).
  • Once the light lands on the chip,
    there is a process employed by the chip, and supporting circuitry, that converts the light into either analog electrical pulses, or digital codes (1’s, 0’s).
    This converted signal is then sent to a receiving device (in this case a TV or video projector) ,
    that will convert incoming electrical pulse (analog) or digital code back into an image that is displayed or projected onto a screen.However, here is where it gets tricky.
    As the camera receives the light reflected off an object at a given point in time and the display device has to present the color of the captured result accurately.

Since neither the capture or display device can reproduce all of the colors that are reflected from the real world objects, both devices have to “guess” based on specific “man-made” color standards, which have at its foundation, a three primary color model. 

In video applications, the three color model is represented by Red, Green, and Blue.

Different combinations of the three primary colors in various ratios are used to recreate the grayscale and all color shades that we see in nature.

Displaying Color via a TV or Video Projector

Since there is no definitive correctness on how humans perceive color in the natural world, and there are limitations capturing accurate color using a camera.
How is this reconciled in the home environment when watching TV or a video projector?

The answer is two-fold, the type of technology used that enables a TV/video projector to display images and color,

and fine-tuning their capability to display color as accurate as possible within a pre-determined color standard.

Here is a brief overview of video display technologies used to display both B&W and color images.

Color Perception,Emissive Technologies

  • CRT – An electron beam originating in the neck of a picture tube scans rows of phosphors on a line-by-line basis in order to produce an image.
    As the beam hits each phosphor, the phosphor is excited and produces the image. Color is produced by red, green, and blue phosphors excited in the proper combination to produce a specific color.
  • Plasma – Phosphors are lit by superheated charged gas (similar to a Fluorescent light). Combinations of red, green, and blue phosphors (referred to as pixels and sub-pixels) produce the designated color.
  • OLED – OLED technology can be implemented in two ways for TVs. One option is WRGB, which combines white OLED self-emitting subpixels with Red, Green, and Blue color filters,
    whereas Another option is to use self-emitting Red, Green, and Blue sub-pixels with no added color filters.