Megapixels

Before explaining what a megapixel is, it is useful to know what a digital image is.

A digital photograph consists of many square small tiles of colour, just like a mosaic. These tiles are very small, and as a result the image appears as a smooth, sharp picture. If you magnify the image a great deal, you start to see the individual squares of colour.

The megapixel rating of a camera refers to how many pixels a camera actually has within its sensor. The 'mega' part of 'megapixel' merely means million. So, a 4 megapixel camera will use approximately 4 million small tiles of colour to produce an image.

As the megapixel count of a camera increases, you can print pictures out at a larger size. For most users, a camera with 4 megapixels is perfectly adequate. You can print an image at A4 size with no noticeable loss in picture quality.

However, if you try to print a poster-sized image you will start to see the image forming into blocks (as in the three pictures below). These are the individual tiles of the image becoming visible.

If you like to edit images by cropping them, it will be beneficial to purchase a camera with a larger number of pixels. As you crop an image, you are effectively losing pixels that can't be recovered, so a high megapixel camera will allow you to have plenty of spare pixels to get rid of. Even pocket sized compact cameras now have 7 megapixels, which is plenty.

Memory usage

As you increase the megapixels contained within an image, you will obviously increase the amount of memory necessary to store that image. Most images are stored in cameras as JPEGs, which is a compressed image format. Below is a rough guide of how many JPEG pictures you can store on 1GB of memory, as the pixel count of the image increases:

Megapixels	No Images stored
2	1180
3	870
4	540
5	400
6	335

The main thing is don't be too concerned about megapixel ratings of cameras unless you are a serious photographer and require a large pixel count.

When choosing a camera, things like the feel and size of the camera, the battery life and the ease of use are more important than how many pixels it has.

Back to Index