3. Resolution
All digital cameras take pictures by chopping the scene you are photographing into a grid of squares, also known as pixels. How many pixels are used depends on the sensor inside the camera, and is usually measured in millions, where 1 million pixels are known as a megapixel, and the number of pixels in the camera is usually referred to as its resolution.
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Most digital cameras currently come in 2 to 12 megapixel versions, though older cameras went as low as a third of a megapixel! So what difference do all those figures make? Simple really! All other things being equal, the more pixels used to make a digital photograph, the finer the detail of the captured image will be. Where this really matters is when you print (or view the shots on a large screen); the more pixels you have the bigger you can print (or view) before the picture starts to look pixellated (fuzzy).
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For a digital print to look like a 'real' photograph you need at least 150 pixels per inch both horizontally and vertically. So for a standard 6x4-inch print the minimum number of pixels in the image needs to be at least 900 (6x150) by 600 (4x150), or half a million pixels. For the best possible quality you really want to print at closer to 250 pixels per inch, which works out at around 1.5 million pixels for a 6x4-inch print. Obviously these figures start to climb as you increase the print size.
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But even if you never print at anything bigger than a postcard, higher pixel counts have their uses. The most important being that they allow you to crop an image – cut out and enlarge a small portion of a shot for better composition – without losing quality. And if you do ever capture a prize-winning shot, you'll be sorry if it's not got enough detail to print at a size you can put on the wall.
Consult the table on page 12 to choose the right no of Megapixels require for your purposes