Images taken with digital cameras and photographs or negatives scanned into the
computer use the term pixels per inch (ppi) to represent resolution; printed images
that are output from printers use the termdots per inch (dpi) to represent resolution.
You can only control one: ppi. The output—dpi—is fixed by your printer. We’ll
explore these terms in the next section.Input Resolution
Scans from a scanner and images from a digital camera come into your computer at
different resolutions. Cameras import images at 72 ppi and scanners import images
at whatever resolution you specify in the scanner software.
The resolution you use to inputimages into your computer might not be the best res-
olution for outputto a printer or the Web. The next few sections discuss input resolu-
tion and how you can change it in your favorite image editor.Digital Cameras and Resolution
Resolution for digital cameras is simple because only two numbers apply—sensor
resolution and output resolution.
Sensor resolutionis the size in pixels of the sensor (for example, 2-megapixel,
4-megapixel, 5-megapixel, 6-megapixel, 8-megapixel, and so on). This is the big
number you see advertised in the paper. The larger the sensor, the higher the resolu-
tion of the image when it’s taken. Table 12.1 contains the approximate resolution of
some digital cameras.Table 12.1 Digital Camera Sensor Resolutions
Sensor Size Approximate Image Size
22-megapixel
(for medium-format cameras) 4056 × 5356
13.7-megapixel 4536 × 3024
11-megapixel 4064 × 2704
8-megapixel 3264 × 2448
6-megapixel 3072 × 2048
5-megapixel 2608 × 1952
4-megapixel 2272 × 1704
3.3-megapixel 2048 × 1536
2.1-megapixel 1600 × 1200
1.3-megapixel 1280 × 960
0.3-megapixel 640 × 480176 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY