CCTV CAMERA RESOLUTION - TVL - Television Lines
Resolution is the quality of definition and clarity of a picture and is defined in lines
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meaning more lines = higher resolution , means better picture quality.
The Resolution depends on the amount of pixels (picture elements) in the CCD chip. If a camera manufacturer can put in more number of pixels in the same size CCD chip, that camera will have a higher resolution. In other words the resolution is directly proportional to the number of pixels in the CCD (Charge Coupled Device) chip.
In many data sheets, two type of resolution, vertical and horizontal are indicated.
Vertical Resolution
Vertical resolution stands for the number of horizontal lines
The Vertical Resolution is limited by the number of horizontal scanning lines. In PAL it is 625 lines and in NTSC it is 525 lines. Using the Kell or aspect ratio factor the maximum vertical resolution is .7 of the number of horizontal scanning lines. Using this the maximum vertical resolution is
PAL 625 X .75 = 470 lines
NTSC 525 X .7 = 393 lines
Vertical resolution is not critical as most camera manufacturers achieve this figure.
Horizontal Resolution
Horizontal resolution = no. of vertical lines
Theoretically horizontal resolution can be increased infinitely, but the following two factors limit this
It may not be technological possible to increase the number of pixles in a chip.
As the number of pixels increase in the chip, the pixel size reduces which affects the sensitivity. There is a trade off between resolution and sensitivity.
If only one resolution is shown in the data sheet, it usually is the horizontal resolution.
Author: Nuttawaj Chieobangyang
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