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Chapter 12: Taking Great Pictures
Microsoft Digital Image Standard User’s Manual
Resolution
Resolution is one of the main factors that determine picture 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 mil
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lion pixels), or in pixel dimensions, such as 1600 by 1200 pixels (which equals
1,920,000 total pixels, or 1.9 megapixels).
Resolution is important primarily because it determines how much you can
enlarge a picture. Everything else being equal, a 3-megapixel picture and a 320
pixel x 240 pixel picture look the same in a wallet-size print. But if you enlarge
those two pictures to 5" x 7" prints, the quality of the 320 x 240 picture is very
low: you can see the individual pixels. The 3-megapixel picture still looks sharp
at the larger size, since its pixels are still too small to be seen.
Resolution is also important because it determines file size. High-resolution
pictures contain color information for many more pixels than low-resolution
pictures, so the files for high-resolution pictures 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 picture 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 com
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mon (but not the only) format for pictures. This is just a general guide to file
sizes—you might produce good printing results by using larger or smaller files.
Approx. JPEG file size
Dimensions Total pixels (with slight compression*) Maximum print size
320 x 240 76,800 23 KB Web and e-mail
640 x 480 307,200 91 KB Web and e-mail
1280 x 960 1,228,800 363 KB 4" x 6"
(1.2 megapixels)
1600 x 1200 1,920,000 576 KB 5" x 7"
(1.9 megapixels)
2,048 x 1,536 3,145,728 970 KB 8" x 10"
(3.1 megapixels)
3008 x 2000 6,016,000 1.5 MB 11" x 14"
(6 megapixels)
* Compression, which is explained in the following section, varies by camera, so you might
find different file size results.