Wednesday, March 30, 2011

Analog, digital and HD resolution

There’s a tendency on the part of some in the machine vision world to believe that everything has gone digital, but that would be incorrect. There are still a large number of analog cameras in use, especially in the surveillance and security world, and analog sales are still significant. However, there are advantages in switching to digital when a system is being upgraded.

To this point, I was recently asked what resolution digital camera should be purchased to equal or improve upon the resolution of a digital camera.

Well do you know the digital resolution of an NTSC or PAL analog TV picture?

The best information I found is on the Axis Communications web site, under the heading “
Resolutions.” This article discusses how to equate NTSC and PAL to VGA, UXGA and also HD TV. There’s also a link to a very interesting paper that gives more detail on how TV picture technology has advanced, along with photos showing how lower resolution progressive scan can yield a sharper image than higher res interlaced.

I also learnt that when I watch HBO I’m viewing a series of 2Mp images transmitted at 30fps. For those of us who know about these things, that’s an impressive number of digital bits being squirted down the cable into my house.

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