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Pop Quiz: Test Your Understanding Of Video Specifications

Test Your Understanding Of Video Specifications 1/02/2005 5:15 AM Eastern

Pop Quiz: Test Your Understanding Of Video Specifications

Test Your Understanding Of Video Specifications

TRUE OR FALSE
  • A nit and a lumen represent the same amount of brightness.
  • All pixels are the same size.
  • Grayscale and contrast ratio mean basically the same thing.
  • The candela is a unit of measurement of luminous intensity based on the light emission from a flame.
  • In XGA resolution, you will not always see exactly 768 lines of vertical resolution.

ANSWERS

1. FALSE. A nit is actually brighter than a lumen. A nit is an amount of light from one square meter equal to one candela (cd/m2). In contrast, a lumen is the amount of light reflecting off one square meter of surface area. The reflection is coming from one candela at one meter. Nits are a measure of direct light and are used to describe the brightness of a display technology, while lumens are a measure of reflected light and are used to describe the brightness of projection technology.

2. FALSE. A pixel has no size.

3. FALSE. Grayscale is the range of gray shades (tones) that can be reproduced by a display from black to white. The more steps in the grayscale, the more shades of color that can be reproduced and the more lifelike the images that are displayed. Contrast ratio is simply the ratio of the brightest part of any scene to its darkest part, or the ratio of the highest light reading produced by a display to its lowest reading.

4. TRUE. Although its definition has changed several times since the beginning of the 20th century, the current definition is the luminous intensity in a given direction of a source that emits monochromatic radiation of 540 x 1012 Hz and that has a radiant intensity in that direction of 1/683 W per steradian.

5. TRUE. This is a result of the Kell factor, which accounts for the fact that the actual visible resolution is only about 70 percent of the number of physical lines. The Kell factor is named after RCA researcher Ray Kell who discovered this phenomenon in 1934.



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