Digital Vs Analog Resolution – Pixels Vs TVL (TV Lines) Explained
One of the most confusing and difficult topics in the CCTV world is resolution. Most of us have digital cameras or video camcorders and have heard the term megapixel used as the most common comparison in resolution between various makes and models. We are also aware that a larger number means better picture quality, but many people do not know why. In the CCTV security camera world, though, most cameras are still analog and their resolution is measured differently from what we are used to. This is slowly changing, but there is still a need for these terms and technologies to be understood by anyone involved in the industry.
Analog Resolution
When measuring analog resolution, a TV line does not have a defined number of individual pixels. Instead, the phrase “TV lines” refers to the number of discernible horizontal or vertical lines on the screen. Analog security cameras are measured in Analog TV Lines, and most of them have between 420 and 580, with a few brands claiming to produce cameras with 630+ TVL. The higher number of TV Lines, the more information captured, and thus the higher resolution and detail in the picture. These types of cameras connect to a security DVR or CCTV VCR, via coaxial video cable, that allows the signal to be recorded and played back later or transferred over the internet..
Digital Resolution
A pixel is the smallest element of a digital image. We have all zoomed too far into a picture from a website and seen the image go from clear to a bunch of colored squares – each one of those squares is an individual pixel. Graphics or images like this can have different resolutions, just like monitors and cameras, and the artists often create work at much higher resolutions than monitors can handle, just so they can be zoomed in or out on without distortion. The most common computer monitor resolutions are 1024×768 and 1280×1024 pixels. Digital point and click cameras like the ones you take pictures of your kids with are usually between 5 and 8 megapixels. Common digital security cameras usually boast a megapixel resolution of between 2 and 3. A megapixel (MP) is 1 million pixels, and is a specific measurement for digital resolution that encompasses the area of the output video (height x width).
Example: If a camera outputs a signal that is 1280×1024 pixels (a standard PC monitor’s resolution), it is shooting at a megapixel resolution of 1280 x 1024 = 1,310,720 pixels = 1.3 Megapixels (MP).
The most common type of digital security cameras are IP Cameras. These, like your digital camera at home, use strictly digital resolution. They utilize a network connection to either act as a standalone device or connect to a network-based DVR (Digital Video Recorder) or NVR (Network Video Recorder). IP Cameras have fixed resolutions and are now approaching, and in several cases exceeding, 1 megapixel in resolution, on average. Many of these cameras also support POE (Power Over Ethernet), which allows them to be powered by the Ethernet cable used for network connectivity, and PTZ (Pan Tilt Zoom), allowing for remote control of the pan, tilt and zoom features, if applicable.
More and more industry installers and professionals are moving to network-based CCTV equipment because of the flexibility and expandability that it allows. Massive remotely-viewable security camera infrastructures are replacing old, out dated analog systems at an increasing rate and will soon become the preferred industry solution.
About the Author
John Hough is a professional lab technician for
ApexCCTV Security Cameras & DVRs
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