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Megapixels, inches and DPI

Digital Photography basics

All electronic consumer product life cycles are continually reducing and it's fair to say that digital photography, or at least the technology employed within the camera, is certainly no exception. While optical developments certainly continue it's the miniature motors and electronics that have driven the digital camera forward and show no signs of slowing down.

As with all elements of photography an understanding of resolution, both for your camera, images and prints is fundamental. Unless that is you are a 'bar bore' who is happy to quote Megapixels, Brake Horse Power etc. with no real knowledge of why, what or how.

So what is a pixel?

A pixel, whether on a screen or print media, is a small square of colour, albeit a colour in a spectrum of millions of other colours but a square of colour none-the-less. Get a group of these pixels together and you can form pictures. If you zoom right into any image you can get down to pixel level. Try it on Photoshop, GIMP or whatever your chosen image editing software.

Okay, so what?s a Megapixel?

A Megapixel is simply a million pixels and the more pixels, or Megapixels that your image or camera has then the more detail, more colour depth and ultimately the larger the picture. More pixels and associated information means larger file sizes too.

So how do Megapixels affect my digital photography?

Well, they do but it depends on your display media. For example a photo for your web site. Taking an average resolution monitor you could expect around 70 to 90 dots per inch (DPI). In the creative media business we work on 72 DPI for online media. So no matter how expensive your photographic equipment it is going to be rendered at 72 DPI to screen.

Okay but is it the same for digital print as for digital displays?

In short no and, er, yes! Digital printing can produce a far greater resolution than monitor screens. As a standard we work on 300 DPI for print. However, unless you want to produce large images (posters, billboards, exhibition stands) your average 3 Megapixel camera will produce more than adequate 8x10 photos for your album or picture frame.

So how many Megapixels is a good camera resolution to buy?

Well, there is no right or wrong answer. Buy what you can afford and that?s suitable for the media type you intend to use. If you?re a web developer then most digital cameras will do, even mobile phone ones included (ish!) However it is better to shoot the original picture in as high a resolution as possible and scale it down. A low resolution scaled up will distort the picture as the pixels are increased, giving the effect like that used to disguise faces on television news! No quite the result you were looking for!

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