A megapixel refers to one million pixels, and is commonly used in reference to digital cameras as an indication of resolution capability. A pixel is a tiny square on a computerized display that is so small it appears as a dot. The display screen is a solid grid of these squares or dots, which can be easily seen with a magnifying glass. The more pixels or dots that make up the display screen, the clearer the resolution or image will be. Greater numbers of dots or pixels allow for more refinement of the image, which results in higher, truer image replication.
When it comes to digital cameras, the picture quality capability is measured in megapixels. For example, a 3.1 megapixel camera can take pictures with a resolution of 2048 x 1536, which equals 3,145,728 pixels. That is, the resulting image will be made up of 3.1 megapixels, or over three million dots. Printers measure quality in DPI (dots per inch). A printer capable of only 300 DPI will not print the 3.1 megapixel image in its native high quality. It's simply not capable of reproducing the fine detail. Instead the image may appear grainy. If you wish to print photos, be sure the printer is well suited to the capabilities of your digital camera.
The number of megapixels required to suit your needs depends on what the camera will be used for, and what size prints are desired, if any. The higher the resolution —- or greater the megapixels —- the more flexibility the camera will have in terms of being able to deliver high resolution prints in large sizes, such as 8x10.
For those who do not wish to print digital photos at all, but prefer to view images on the computer or television display, purchasing a high megapixel camera is not required. Even 1.5 megapixels will suffice. That said, most cameras as of fall 2005 are 3.1 megapixel or better.
If you are planning to print pictures in sizes up to 8x10, experts recommend a camera with 4-5 megapixels, or a resolution of about 2500 x 2000. For prints up to 12x16, look for resolutions of 3200 x 2400 or better, which translates to a 6 megapixel camera or greater. As a comparison, many professionals use 11 megapixel digital cameras for maximum resolution and clarity even in large printed displays. If you don't plan to print enlargements, paying for more megapixels than you need will be a waste of money.
Aside from the megapixel rating of the digital camera, the amount of internal memory and type of flash card can make a big difference in convenience and long-term cost. Larger internal memory allows for more flexibility, as does the ability to use flash cards with higher capacities, though those with lower capacities will be less expensive.