What is a megapixel? (From Salisbury Journal)

What is a megapixel?

3:24pm Tuesday 14th November 2006 in Your Computer

Megapixel is the term used to describe a million pixels in relation to digital cameras. A pixel is a minute point, (a dot), within the photo which has its own colour. All else being equal, (more about that later), the more pixels, (or megapixels), the better.

When printing an image you should expect to print at least 150 pixels per inch in order to produce a realistic image.

This means that to produce a 5 x 7 inch print, less than 1 megapixel will suffice. 5x150 = 750 pixels high, 7x150 = 1050 pixels wide (assuming landscape). 750 x 1050 = 787,500 pixels in total (0.8 megapixels).

If your printer can print at 300dpi (dots per inch or pixels per inch) then you need four times the number of pixels (twice as many in each dimension).

This means that if we wish to print images in larger formats and good quality then we need a lot of pixels. An A4 print at 150dpi needs 2.2 megapixels whilst to print the same image at 300dpi would require almost 9 megapixels!

You might be forgiven for thinking you only need to worry about getting more megapixels but in reality the quality of the lens and the size and quality of the sensor in the camera (the CCD or Charge Coupled Device) which replaces the film in traditional cameras make even more difference. Life's never simple is it?