A good lens gets the most out of a high-megapixel count camera.
When buying a digital camera, the first number most buyers look at -- and in some cases, the only number looked at -- is the number of megapixels provided. Megapixels are one factor to take into consideration when buying a camera or using a webcam, with almost no downside and several advantages. A high-megapixel count doesn't guarantee good photography on its own.
Pixel Definition
A pixel is a coordinate on a grid with a color value assigned to it; computer screens have their resolution expressed in pixels, as do high definition televisions. An HDTV is made up of 1,920 pixels of width by 1,080 pixels of height. A megapixel is 1 million pixels, and the megapixel rating of a display, or a camera sensor, is taken by multiplying the number of pixels in width and multiplying by the number of pixels in height, and dividing the resulting number by 1 million. For example, an HDTV display is 1.9 megapixels. A 640-by-480 low-end Web cam is 0.3 megapixels.
Megapixels and Printing
Print photography has two thresholds for megapixel displays. Color printers have a dots-per-inch resolution, which will be, for a typical desktop color printer, 300 DPI. This means that a 300-by-300 pixel area translates into a 1-by-1 inch printed image. At this resolution, 6 to 7 megapixels translates into an 8-by-10 inch full-color print. For offset printing and professional photography, the production process allows 600 DPI, which means that, in theory, a 12- to 15-megapixel camera can get better results than a 6-megapixel camera. In practice, unless you're printing poster-sized prints, you may never notice.
Megapixels and Monitor Display
Most digital photographs never get printed; they get displayed on computer monitors. While some computer monitors go to 2,560-by-1,600 pixels, that's only 4 megapixels, and you won't be showing the image at full screen on a computer monitor. The most common picture size displayed on computer monitors is 1.3 megapixels, which is 1,280-by-1,024 pixels, and 0.3 megapixels, which is 640-by-480 pixels; 0.3 megapixels is used for video chatting.
Megapixels and Photo Editing
Photo editing is where high-megapixel cameras shine. One of the truths of photo manipulation is that you can take pixels away, but adding them back in is a challenge. Even if you are planning on doing casual 300 DPI printing, starting out with a large image and cropping out the parts you don't need, or doing other photo manipulations, is easier when you have more pixels to work with.
Megapixels and Good Photographs
There are two tiers of cameras -- casual cameras without interchangeable lenses, and professional cameras that can use 35 mm SLR lenses and Micro 4/3 interchangeable lenses. Once you get past roughly 5 to 6 megapixels, good lenses -- and the skill of the photographer -- are needed to get full use out of a higher resolution camera.
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