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This chapter is from the book

Resolution? I Resolve to Explain...

The term resolution comes up every time I talk about cameras or scanners, and even monitors and printers. Resolution refers to the quality of the image produced by a camera or scanner, displayed by a computer screen, or created by a printer. Resolution measures the number of dots or pixels (which stands for picture element, the preferred term for dots on the computer screen) per square inch of image. A higher resolution means that the image is made up of more, smaller pixels per inch.

When you look at a picture on your computer or television screen, you’re looking at a bunch of relatively large colored dots. (The typical screen resolution for an inexpensive monitor is 72 dots per inch, abbreviated as dpi.) Each dot measures 1/72 of an inch across. Your eye and brain work together to blur the dots into an image. Each dot or pixel has slightly different amounts of the red, green, and blue phosphors that give off light in those colors. They mix visually to make each dot a different color.

If you’re familiar with the paintings of Georges Seurat, the famous pointillist painter, you’ll remember that he placed tiny, individual dots of color on his canvas. Because you can actually see the little dots and count them, his paintings are at a very low resolution. He was probably working at about 25 dpi, or 625 (25 squared) little dots of paint per square inch of canvas. With patience like that, he should have been a scrapbooker. Figure 3.1 shows a greatly magnified view of a small piece of a Seurat painting. As you can see, every dot is a different shade of color, translated by your eye and brain into a unified image.

Figure 3.1

Figure 3.1 This is blown up to show the dots better. (Georges Seurat, "Sunday Afternoon on the Island of La Grande Jatte")

A similar kind of dot is found on the sensor, the "film" part of the digital camera. These sensor dots analyze the light that falls on them, determining its percentage of red, green, and blue. Then the digital camera records this info along with the position of the dot in the captured image. That gets to be a lot to remember. So when you upload the picture to the computer from the camera, all that information is included. The more pixels per square inch you have to deal with, the higher the resolution of the image, and the more memory it takes to hold it all. So, higher resolution means bigger files as well as better-quality pictures. Of course, it takes more time to open and process a large file. It takes more storage space, both on the camera’s flashcard and on the computer itself, to save them. You can actually save a little money here by not buying more camera than you need. Think about what you want to do with it other than scrapbooking, and whether you really need 5-megapixel resolution. If you’re going to be shooting outdoors, in a variety of lighting situations, it’s more important to find a camera with a flash and a zoom lens.

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