Digital cameras have reshaped photography and have rapidly displaced film cameras for most casual and professional jobs. Digital cameras range from $50 to $200 ultra-compact, point-and-shoot models to Digital Single Lens Reflex (DSLR) cameras that cost $1,200 or more for the camera body alone. While there's more to taking good photographs than the camera, a good camera makes it easier. The trick is finding the balance of features and price that fit your needs.
Megapixels and Price
Cameras are sold on the basis of megapixels, because it's a single number that makes comparisons easy -- more megapixels is, theoretically, better. Or at the very least, more megapixels equals a higher price and a larger number to justify it. The reality is that megapixels give you more freedom for cropping out the parts of the image you don’t want to see after you've processed the image. According to David Pogue of the New York Times, the only benefit of a camera with more than six megapixels is if you're producing very large prints for public display.
Optics and Zooming
Camera optics are more important than megapixels, and higher-quality optics will drive camera prices higher faster than megapixels will. The cameras with stratospheric prices have, in general, professional-grade optics. Better optics (a higher degree of optical zoom) makes it likelier that what you're photographing will be in focus and using most of those pixels. Don't confuse "optical zoom" with "digital zoom." Digital zoom works exactly the same way as the zoom slider on your photo editing program.
DSLR Versus Unibody Cameras
A very significant price jump occurs in cameras when you switch from integrated-lens cameras to ones that can use interchangeable lenses, whether using the DSLR standard or the newer Micro 4/3rds system. The benefit of using interchangeable lenses is that you'll get more detail at a specific focal length and distance from the subject, but the position of the camera relative to the subject will matter more. While you can take sharper, clearer photographs, the background of the image will be less focused, and small changes in position and lighting can make a big difference. An interchangeable-lens camera requires more photographic skill to use but can reward more skill in the photographer. Interchangeable-lens cameras also mean a heavier, larger camera and the need to swap lenses (or to swap settings on a more complex lens) than a simple point-and-shoot pocket camera will have.
Sensor Size and Depth of Field
Depth of field is the focal plane of the camera -- the range of distances at which, given a particular lens, the subject of the camera is in optimum focus while the background (and foreground) loses detail. Larger sensors give a much shorter depth of field but give a much sharper focus in that depth of field. Smaller sensors, like on most point-and-shoot, small-body cameras, can't get the same degree of focus on the subject but are much more forgiving of relative distance from the photographer to the subject. It's no surprise that DSLR cameras, with interchangeable lenses, tend to have "full frame" sensors, and those larger sensors drive up the price and make for better images if used by a skilled photographer.
Camera Speed and Image Stabilization
Camera speed is a function of the internal optics and the quality of the sensor; a higher-speed camera is capable of taking shots of objects in motion without them becoming blurry. While camera speed doesn't have a common set of marketing metrics, it is one of the places where cheaper cameras are noticeably worse than more expensive ones. Image stabilization uses a free-floating lens in the optics and gyroscopes to adjust the image on the side; in 2010, it was an expensive option. By late 2012, the price has dropped considerably and should be something you look into as well.
- CNET: Digital Camera Buying Guide
- Cambridge in Colour: Camera Sensors Tutorial
- Photo.net: Depth of Field and the Small-Sensor Digital Cameras
- Camera Technica: The Science of Image Stablization
- Digital Photography School: Should You Buy A DSLR or Point & Shoot Camera?
- New York Times: Breaking the Myth of Megapixels
- PhotoXels: Optical vs. Digital Zoom
- Sean Gallup/Getty Images News/Getty Images