Understanding Digital Camera Resolution

The term "Resolution", when used to describe a digital camera refers to the size of the digital image the camera produces, and is usually expressed in terms of "megapixels" or how many million pixels it can record in a single image.

For example, a camera that captures 1600 x 1200 pixels produces an image with a resolution of 1.92 million pixels and would be referred to as a 2.0 megapixel camera. You get to 1.92 million pixels by multiplying the vertical and horizontal dimensions. That number is then rounded off to 2 for marketing purposes.

• More resolution means better quality - up to a point! Both optics and the quality of the image capture chip play a role too.

• The advantage of having a camera with a higher resolution is you have more pixels to work with. That's a big plus when getting prints made.

• Remember, you can produce a printout from just about any image, but the more you have to blow it up the more you degrade the quality.

Computer monitors display images at 72 ppi (pixels per inch), meaning that there are 72 pixels for every 1 inch of linear screen space you see on your screen.

Therefore, if you have an image on the screen that is 720 pixels wide, it will take up 10 inches of linear screen space (72 dpi x 10 inches = 720 pixels).

This may look beautiful on the screen, but if you try to print this image on a printer at 72 dpi the result will look extremely choppy and jagged.

To get a good looking print from your printer you'll need to print at 300 ppi (pixels per inch), which means that the 10 inches across the screen will be reduced to only 2.4 inches on paper (720 / 300 = 2.4, or 24% of the original 10 inches).

1,200 pixels ÷ 72ppi = 16.6 inches

On paper that same image would be 4 inches wide.

1,200 pixels ÷ 300ppi = 4 inches

How many image pixels you need depends on the size of the print you want to make. As a rule, you need a minimum of 300 pixels for each linear inch of the print. For example, a good 4-x-6-inch print requires 1200 pixels horizontally by 1800 pixels vertically, or a total pixel count of 2,160,000, which is just over 2 megapixels.

Because the aspect ratio (width relative to height) of a digital photo is 4:3, which is different from the traditional frame sizes shown in the Table, your camera probably doesn't offer the specific pixel dimensions shown in the table. As long as your camera has a pixel count that's equal to or higher than the numbers shown here, you'll be set up for good print quality.