Q: What is a megapixel CCTV camera?
A: It’s a camera with a sensor that has a million pixels or more. For comparison, a CIF image has around 100,000 pixels, and a 4CIF image around 400,000 pixels.
In practice, megapixel cameras usually start at 1.3 million pixels, so in theory even a basic model can deliver pictures with three times as much detail as a 4CIF camera.
Q: Why is the extra detail useful?
A: It means you can zoom into the picture much more before the image starts to break up.
This means, for example, that in a petrol filling station with four lanes you might use a single megapixel camera to cover all of the lanes, instead of four standard cameras covering one lane each.
This one camera could capture as much detail as the four standard cameras put together, saving on installation costs and cabling.
Q: So is it a good idea to fit megapixel cameras wherever possible?
A: No. Because megapixel images contain more detail they take up more storage space on DVRs and they use more network bandwidth.
Recording the images for a month from just one megapixel camera at 12 fps using the most efficient H.264 compression takes about 500 GB of storage. That’s three or four times as much as would be needed for a 4CIF camera.
The same sort of factor applies to network bandwidth requirements, so using megapixel cameras where they’re not needed can significantly increase costs.
They can be very useful, as the petrol forecourt example shows, but only if more detail is required or a cost saving achieved through using fewer cameras.
Q: Is there anything else to look out for when using megapixel cameras?
A: Yes. Because the individual pixels on the sensor are smaller than in ordinary cameras, they don’t perform as well in low light.
Also, it’s essential to use a lens that’s designed for megapixel applications. Industry standard lenses are fine with ordinary cameras, but they don’t reproduce the sharp enough images required by megapixel sensors.
Finally, don’t forget that a typical screen resolution of 1280 by 800 is only just one megapixel, so users will only see the full benefit of the more detailed images when they zoom in.
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