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Microsoft Picture It! Companion Guide
9
Chapter 2: Making the Most of Your Camera
The number of pixels that make up a photo is the photo’s resolution. Resolution
and compression are key factors in determining the quality of a digital photo.
The following sections explain resolution and compression.
Resolution
Resolution is one of the main determinants of photo quality since it is a
measure of the total number of pixels that make up a photograph. Resolution is
sometimes expressed as the total number of pixels, such as 3 megapixels (3
million pixels), or in pixel dimensions, such as 320 x 240 (which equals 76,800
total pixels).
Resolution is important primarily because it determines how much you can
enlarge and print a photo. Everything else being equal, a 3-megapixel photo
and a 320 pixel x 240 pixel photo look the same in a wallet-size print. But if
you enlarge those two photos to 5” x 7” prints, the quality of the 320 x 240
photo is very low: you can see the individual pixels. The 3-megapixel photo
still looks sharp at the larger size, since its pixels are too small to be seen.
Resolution is also important because it determines file size. High-resolution
photos contain color information for many more pixels than low-resolution
photos, so the files for high-resolution photos can be significantly larger. File
size becomes an issue if you have limited storage on your camera or hard disk,
or if you need to send the photos through e-mail.
The following chart gives an estimate of file size and maximum print size for
various resolutions. The chart lists file sizes for JPEG format, which is a
common (but not the only) format for photos.