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What is a Megapixel?

An important question for understanding digital cameras

what is a megapixel what is a megapixel

Ok, what is a megapixel!? It's certainly a favourite talking point of camera salespeople, but what actually are these pixel thingies and why are they so important to photography?

Even if the importance of megapixels, or MP's, is sometimes overstated, there's no doubt they are key to understanding digital cameras.

So I want to give you some basic digital camera facts on this subject, to help you negotiate the jargon that gets thrown your way when choosing a camera!


What Is a Megapixel? The Short Answer!

A megapixel is 1 million pixels. Simple! Pixels themselves are the little individual elements that make up a digital image. The word 'pixel' itself is merely a combination of 2 familiar words: 'picture' and 'elements'.

In digital cameras the pixels are located on the image sensor which sits inside the camera body. Megapixels are the measurement used, as opposed to just pixels, because it's easier to talk in small numbers.

So basically, a MP is a measure of resolution, or detail.


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What is a Megapixel? The Slightly Longer Answer!

Now for a little bit of background. The concept of picture elements came out of the early days of TV. It related the picture quality of moving images on television screens.

This concept was first expressed in its abbreviated form, 'pixel', in 1965 in reference to video footage being sent back from space probes on Mars and the Moon!

Pixels now refer image resolution in a whole range of digital devices. Sometimes this can actually lead to a bit of confusion. But essentially, a pixel is seen as the smallest single element of a digital image.

So the more pixels in an image the greater the detail and accuracy will be. That's why it's an important part of understanding digital cameras. Resolution is important to image quality and potential print size.

What actually are the physical pixels on a digital camera sensor? Well, I don't want to delve into excessive technical detail, but they are basically 'photosensor elements'.

These react to the light and create an image electronically, as opposed to chemically with film. The images are then saved on to a memory card and the image sensor can be used again and again, unlike film.

Megapixels are not always stated as a straight number, e.g 12MP. Often 2 numbers are used, to refer to the pixel count along the horizontal and the vertical, e.g 3872 x 2592. So in this example there would be 3872 pixels across the horizontal and 2592 along the vertical (in a landscape format); that's 10MP in total.

Sometimes people get confused between pixels, which are often expressed as 'ppi'/pixels per inch and 'dpi'/dots per inch. 'Dpi' is something different entirely. It relates to the technology of inkjet printers and how many droplets of ink they can spray on to a sheet of paper in the space of one inch.

'Dpi' is the detail of a print, which works on the CMYK colour system. Ppi is the reloution of a photo, which works on the RGB colour system. So remember they are separate things.


How Important Are Megapixels?

As I mentioned, MP's are crucial to understanding digital cameras. They are one of the key digital camera facts worth getting straight when buying. More pixels enable you to print nice big posters of your shots. (Tips on printing digital pictures)

When images don't have enough pixels to be successfully printed at a certain size, the individual pixels start to become noticeable. This is called 'pixilation', and it's ugly.

what is a megapixel what is a megapixel

Having said this, the zeal with which manufacturers have pursued ever greater numbers of MP's for their cameras could give a false impression of their significance.

Many keen photographers rarely need great big poster sized prints and there are lots of other things that contribute to image quality.

For example, if you're a DSLR user I'd recommend saving some cash on fewer MP's with your next upgrade, and spending it on a brilliant lens (Tips on find the best digital camera lens). The quality of a lens has a big impact on image clarity.

So there's more to life than megapixels - but they are important!

Still have questions about 'what is a megapixel'!? Feel free to ask me.

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