Resolution Explained: Megapixels, DPI, and Tips for Sharing Digital Photos

Digital cameras have steadily increased in image quality since first coming on the market. Knowing something about resolution proves helpful when editing your digital images, as well as when printing them out for family and friends.

Pixels and Megapixels Explained

Pixels are tiny squares of color, grouped together, to form the digital image we see on a computer screen. If you use the zoom tool in any image editing program to zoom in on a photo, you’ll begin to see your picture turn into squares. The closer the zoom, the less picture-like it seems, and the more it resembles a Rubik’s cube. One "megapixel" is equivalent to 1 million of these pixels.

As a general rule in the digital world, the more pixels an image has, the more detail. This also means the image file size will be larger, and print size will be bigger. More pixels offer more shades of color, giving it a more realistic look.

The average user doesn’t need more than 3.2 megapixels. Why? Your computer screen is only capable of showing 72 to 96 dpi, or dots per inch. Any monitor, even the most expensive, high-end models, can’t show more than that due to the mechanics of the monitor itself. If your digital camera is capable of shooting images at 1280 x 1024 pixels per inch (also called resolution), your monitor can still only show you 72 of those.

Printing Digital Photographs

With a 3 megapixel camera, you can print out an 8x10 or smaller and still get good results. This is generally as large as the hobbyist photographers will require. On prints of this size, you'll need specially sized paper, as well as a printer capable of handling the larger paper format. Most jobs that require this are best taken to a professional printing shop.

However, if you wish to print the photos, you must keep them at the larger, pixel-heavy resolution. Printer software converts pixels into ink drops, and printer resolution is measured in dpi, or dots per inch. The higher the dpi, the more ink in a given space, and therefore more detail or color shown on paper.

All photographs need 300 dpi or better to look good on plain 20-lb. paper, or even the thicker photo paper (the type of paper you use to print your photos also has a great effect on quality). If you print an image taken at 3 megapixels, you’ll get an 8x10 image. If you use a 2 megapixel camera, you’ll get a good quality 5x7 print. If you’re using a 1.2 megapixel, you’ll get maybe a 3” wide print; lower resolutions such as this are good for Web pages and email use, but seldom contain enough detail for a clear print. 

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