9.2: The Basics

Digital camera sales continue to grow each year with millions of units flying off store shelves. The advantages of a digital camera over a traditional film camera are many, including:

• You can take as many pictures as you want and see right away if you got the picture you want.
• You can upload pictures to your computer and share them with friends and family anytime via the Web.
• You don’t have to buy film, and you don’t pay to print photos you don’t want, so you save money.

Many fields use digital photography every day, including police officers, fire fighters, real estate and insurance agents, scientists, doctors and dentists.

The key to understanding how to work with digital photographs is all in the pixels. Pixel is a mashed-up word meaning PICTure ELement and is usually imagined as a tiny square on a matrix overlay on a computer image. A pixel is the visual representation of data in a digital image or graphic. To picture this in your mind, think of a mosaic where a photograph is composed of hundreds or thousands of tiny squares.

If you are shopping for a digital camera, the first measurement you’ll use to narrow your choices is the megapixel. A megapixel represents one million pixels. It is used to measure the power of digital cameras with some simple math. For example, a standard digital camera is rated at 3.2 megapixels because the largest photographs it can capture are 2,048 pixels wide and 1,536 pixels tall and 2,048 x 1,536 = 3,145,728 (and the manufacturers round the number up for marketing purposes). If you used all the information in a 3.2 megapixel image, you could print a high-quality photograph that is roughly 5 x 7 inches.

Cameras store photographs as digital files on a memory card (see box for more information). The more pixels in a photograph, the more bytes needed to store the picture. Cameras can be adjusted to lower the number of pixels captured to save space on the memory card, but now that large memory cards of 512MB or even 1GB are so cheap, it’s rarely necessary.

About Compact Flash and Secure Digital memory cards:

A memory card is a critical component to digital photography: It's the thing that holds the pictures. Essentially it’s like a reusable disk for storage. The most popular types of flash memory cards for use in digital cameras are: Secure Digital (SD), Compact Flash (CF), Memory Stick (MS), MultiMediaCard (MMC), xD-Picture Card (xD) and SmartMedia (SM).

Now that you understand pixels you can begin to get your head around resolution. When it pertains to the display of electronic data, resolution is a measurement of pixels that are available to the human eye. Computers have displays that can be adjusted to show more or less information on the screen. (A common display setting is 1024 x 768.)

When it comes to photographs, resolution refers to the number of pixels in an image. Since most computer monitors display 72 pixels per inch (ppi), photographs on Web sites only need a resolution of 72 ppi. Photographs in a printed newspaper are usually 200 ppi and a glossy magazine uses images at 300 ppi.

A photograph will be much larger in bytes at 200 or 300 ppi, and therefore will eat up more computer processing time to upload or download and will not display any sharper on a 72 ppi screen. So there’s no reason to make users wait for the longer download for the higher resolution image. This is the problem when a reporter finds a photograph on a Web site and would like to include it in print. The low-resolution image doesn’t scale to 200 ppi and will look blurry, especially if it is enlarged.

Conversely, if you have a high-resolution image for publication on a Web site, it should be compressed. Compressing an image means using software to squeeze the image, omitting the pixels that aren’t necessary and making the file smaller (in bytes) without sacrificing the overall quality.