How Many Pixels Are Enough? A Guide to Choosing a Digital Camera

The first thing people want to know about a digital camera is "how many pixels does it have?" Although this is not a bad question to ask, it's not the only factor to consider when choosing a camera. To help you decide how many pixels you need (and how much money you need to spend to get those pixels).

The first thing people want to know about a digital camera is "how many pixels does it have?" Although this is not a bad question to ask, it's not the only factor to consider when choosing a camera. Cameras with higher pixel counts generally create higher quality pictures, but they also create larger files that aren't appropriate for some uses.

For example, if you're purchasing a camera to use primarily for sending snapshots via e-mail or the Web, you have to resize your images to a smaller size to reduce upload and download times. You don't need a 3-megapixel camera if you'll always resize the images down to a megapixel or less.

Counting pixels

If you plan to print most of the picture you take with your digital camera, you want as many pixels as you can get. This is especially true if you'll be printing your images on a high-quality photo printer. The larger the print, the more pixels you need to get an acceptable picture. Table 3.1 shows how many pixels you need for several popular print sizes.

Approximate Number of Pixels Needed to Produce a High-Quality Print at Different Paper Sizes

Megapixels ----- Maximumm Print Size

1.3 --------------- 4 x 6''

2.0 --------------- 5 x 7''

3.3 --------------- 8 x 10''

5.0 --------------- 11 x 14''

Many people-including camera manufacturers-often incorrectly use the term resolution to refer to the pixel count, or the number of pixels produced by a camera. Resolution refers to the camera's ability to capture small details. Pixel count is simply the number of pixels produced by the camera's image sensor. Although the two terms are related, they're not the same.

Is More Always Better?

The short answer is yes. All things being equal, a camera with more pixels produces better pictures than a camera with fewer pixels. The pixel count determines the overall size and quality of the images created by a digital camera. In general, the more pixels, the more detail a picture contains. Pictures with more details appear sharper than pictures with less detail.

Printer technology is improving almost as fast as camera technology. As discussed in Chapter 9, "Inkjet Printers," inkjet printers (the most popular type of printer for printing digital camera images) print images using tiny dots of ink. The more dots the printer can produce, the clearer the image appears.

Just a few years ago, 600 dot per inch (DPI) printers were the norm. Today, there are several inexpensive printers on the market that can print more than 2,000 DPI. These new printers take better advantage of the increased pixel counts and higher detail of newer digital cameras.

In a film camera, picture quality is a factor of the size of the film, the sharpness of the lens, and the resolving power of the film. In a digital camera, resolution is determined by the number of pixels in the image sensor, the sharpness of the lens, and the camera's ability to convert raw pixels into an electronic image. In the film world, the easiest way to get more detail is to use a larger piece of film. In the digital world, you get more detail by creating more pixels-up to a point, as you'll see in a moment.

Pixel count has become the main yardstick used to measure and compare cameras. Digital cameras produce images with millions of pixels, so the term megapixel is used as shorthand for "a million pixels."

To understand what pixels are and why they're important, it helps to understand how conventional film cameras work.