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What does 420 TV Lines stand for on a security camera

By yyiiyyii
Aug 12, 2007
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  1. What does 420 TV Lines stand for on a security camera? How does 420 relate to pixels or resolution. Also what is the resolution of a standard camcorder
     
  2. captaincranky

    captaincranky TechSpot Addict Posts: 11,055   +970

    Rank and File....Horizontal by Vertical.....

    TV resolution is measured by rank and file. Therefore a TV picture of 720 x 480 would have 720 dots going across the horizontal axis of the screen, and 480 dots on the vertical axis. These rows of dots would describe rows of pixel points 720 rows of dots from the horizontal, ( these rows would actually run from top to bottom VERTICALLY)! Then the 480 lines of vertical resolution would actually run HORIZONTALLY from side to side of the screen. Basically, what is being described is a matrix. Picture a checkerboard with 720 squares in 1 direction and 480 squares in the other. The total number of "pixels" in the screen would simply be 720 multiplied by 420, which equals 345,600.
    In the reproduction of a color picture by a CRT each "pixel" actually consists of 3 apertures in a screen, each being targeted by one of three different color "guns", a red, blue, and a green.
     
  3. jobeard

    jobeard TS Ambassador Posts: 13,516   +336

    TV pictures are created by (originally) a crt electron beam SCANNING from
    upper left, horizontally to the right and moving down until it reaches the lower right
    of the screen . 420 Lines means that it take 420 scans to get the job done.
    This is repeated 60 times per second.

    The more LINES, the better the picture; this is what HD tv is all about too :)
     
  4. yyiiyyii

    yyiiyyii TS Rookie Topic Starter Posts: 108

    what is the most lines u can have? does 420 sound like there would be a clear picture? how many lines did a standard camcorder have befpre they went digital

    i had a security camera where u couldnt see the person face from 20 ft away and i had a old camcorder where u could see the person face from 20 ft away.

    so my real question is would u be able to see a clear picture of a persons face from 20 ft away
     
  5. captaincranky

    captaincranky TechSpot Addict Posts: 11,055   +970

    Lines, what lines........I forgot my lines!.....

    There is more to the issue than lines of resolution. Most important are quality of optics, and type and quantity of light present. Sufficient light gets rid of noise in video sensors thereby increasing apparent resolution. Using crappy lenses should speak for itself. At the end of the day security cameras that work well cost much. I believe that the standard NTSC TV resolution of 680 X 480 lines is about what a decent security should spec to.
     
  6. Mictlantecuhtli

    Mictlantecuhtli TS Evangelist Posts: 4,919   +9

    420 lines means the image would look sharper than TV, because the TV image is interlaced, ie. 240 or 288 lines / 25 or 30 times a second.
     


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