Megapixels Explained

Confused by all the lingo, Want to know what a megapixel is, and why its important?


Camera resolution is defined as the amount of detail that a CCTV camera can capture. Resolution is measured in pixels. A higher number of pixels, means more detail and larger images without blur or being grainy. Resolutions are measured in Megapixels, which is just over one million pixels, 1,048,576 to be precise. The horizontal resolution is multiplied by the vertical resolution to arrive at the total value in megapixels.

In layman's English please

A typical 22" Computer monitor with a typical PC displays what's called 1080p, or 1920 x 1080.

This sits somewhere in between a 2mp and a 3mp camera's resolution.

So what happens when the standard camera installed by Argon Security is 4mp, is it really much clearer on this typical monitor?

The short answer is no! But....... The picture from the 4mp camera is physically bigger than the monitor can display, so in order to show the whole scene, some compression of the image is applied to show a full size image. The original 4mp image is still recorded to the Hard Drive, and will be far superior when we need to playback the image and zoom in to a particular area of interest.

Think of it this way, you can not zoom in on a 2mp camera on this monitor without some pixilation of the image. but you could zoom a 4mp camera in 2x before screen pixilation would occur.

So whats all the Compression mumbo jumbo about?

Compression is all about how big an image is in data size, not the physical size. When we talk of a 4mp image, we talk about the image being 2688 x 1520 dots, but we do not talk about how much hard drive space we need to store this image and that is where compression comes into the equation.

CCTV cameras use a number of tricks to reduce the hard drive space needed without making the physical size of the image smaller. A 4mp image (2688 x 1520) can have different compressions applied to it, but the size of 2688 x 1520 will not change.

What does change is the size of storage needed. h264 and h265 are the current standards.

Lets compare how much disk space is required if we record 2 cameras, both 4mp, but set to different compression settings.

Camera 1, 4mp (2688 x 1520), compression h264 = 30mb

Camera 2, 4mp (2688 x 1520), compression h265 = 17mb

So by using h265, we save nearly half the hard drive disk space, or the other way to look at this, on a 6tb Hard drive h265 would give us nearly twice as many days for the same quality picture.