Most cameras come with a skimpy 16-megabyte memory card, enough to hold a handful of 2-megapixel images but perhaps only one 5-megapixel image. The downside of pixel-rich pictures is the way they fill a camera's memory. Whether you crop in your computer or with your camera's digital zoom, the quality of your results will depend on how many pixels your camera used to make the image and how much of that image you crop away. On the other hand, such cameras are mainly used for snapshots, and for snapshot-sized photos, sometimes digital zoom isn't too bad, said Sally Smith Clemens, a product manager at Olympus. Entry-level cameras are also, alas, likely to have lower pixel counts to start with. Digital zoom is not as valuable for cameras that have zoom lenses as it is for entry-level cameras that don't, said Chuck Westfall, director of technical information for camera products at Canon. It is like cropping your picture in your computer, only with less time to select your composition and no chance to change your cropping if you do not like the result. Do not confuse this process, optical zoom, with so-called digital zoom, a purely electronic process that selects a small subject area by throwing away the surrounding pixels: the pixel count of the area you select with digital zoom has the same pixel count as before, so you do not gain anything but a tighter composition, and the picture may look fuzzier. The picture area contains just as many pixels as before, but with more of them now devoted to the subject area you want, its details are clearer. A zoom lens does this by narrowing its view to exclude some subject areas while magnifying whatever is left within the frame. It is also possible to crop within the camera, zeroing in on an important subject area so that it fills as much of the frame as you want. That might be a worthwhile trade-off if it reduces a 5-megapixel image to 3 megapixels, but not so if the image goes from 2 megapixels to a paltry 1.2. ![]() Crop out 40 percent of your picture, though, and you lose 40 percent of its pixels. Pictures that looked good when you shot them may contain distracting elements cropping allows you to prune those elements away and make the picture stronger. Few amateurs make prints that big, but another reason to go for a higher pixel count is the ability to crop. In prints larger than 8 by 10 inches, differences in pixel counts become more noticeable. I'll make 8-by-10's all day long from that. Most people will never, ever need something above 3 megapixels, said Jon Sienkiewicz, the vice president for marketing at Minolta. This was not always true, but current digital cameras do a better job of processing the raw data from their image sensors into image files on their memory cards. For prints measuring up to 8 by 10 inches, or 20 to 25 centimeters, the difference between shots with 2 megapixels and 5 megapixels can be hard to discern. For prints, more resolution is required, and the bigger the print, the greater the difference the pixel count makes. For sharing by e-mail, an image size of 640 by 480 pixels, or 0.3 megapixel, is usually best: large enough to look sharp on a computer screen but small enough to upload or download quickly. How many megapixels you will need depends on how you plan to use your images. Those numbers are no match for 35- millimeter film, which has a resolution equivalent to 20 megapixels or 30 megapixels, but digital cameras can nonetheless produce excellent images. Digital cameras made for amateurs usually have between 2 megapixels and 5 megapixels, though cameras with 8 megapixels or more will be available soon. An image 2,048 pixels across and 1,536 high has just over 3.1 megapixels a 2,560 x 1,920 image is just over 4.9 megapixels. A digital camera's effective pixel count is its horizontal resolution multiplied by its vertical resolution. The more there are, the sharper and more detailed the picture is, and the harder it is to distinguish the elements from one another. A good photo usually has millions of these elements. All photos are made up of tiny elements: from the ink dots in newspaper photos to the grains of silver or particles of color dye in film photography. But what are megapixels? How many do you need? Is more always better? Pixels, known as megapixels when you count them by the million, are picture elements, the tiny spots of data that make up a digital image. The higher the number of megapixels, the more expensive the camera will be in comparison with others with similar features. The more megapixels the merrier or so you would gather from digital camera prices.
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