Answers to your multimedia questions.
Q I'm upgrading my digital camera and want to get as many megapixels as I can so I get the best picture quality. What is the most megapixels I can get in a superzoom camera?
A Most of them top out around 14 megapixels these days, but megapixels is a poor predictor of picture quality. An older 6-megapixel digital SLR will easily outperform a new 12-megapixel compact or superzoom.
Three parts of a digital camera work together to create images: the lens, the sensor and the "jpeg engine." The lens gathers and focuses light on the sensor. The sensor reads the light and sends digital data to the camera's computer (containing the jpeg engine), which processes the raw data from the sensor to create images. There is a technique using the unprocessed, raw data from the sensor, but it is used mostly by pros and advanced amateurs and will be covered in a future column.
A megapixel is 1 million pixels, or picture elements. A pixel is one light-gathering cell on the sensor, so a 10-megapixel camera has 10 million individual light-gathering cells.
More megapixels mean higher resolution, which at face value would seem like a good thing. Unfortunately, it is more complicated than that.
Most consumer cameras have sensors with tiny physical dimensions and small surface area. That means that if you go from 8 megapixels to 12 megapixels, each one of those light-gathering cells has to be a lot smaller to fit on the tiny chip. Smaller cells gather less light and the camera's computer compensates by amplifying the signal. This often leads to grainy, overly contrasted pictures in all but perfect lighting conditions.
The constantly climbing megapixel count has been driven by marketing, and photo buffs have been complaining about the "megapixel race" for years. Manufacturers are starting to take note. High-end compacts now have lower megapixel counts than they did a few years ago, and picture quality has improved as a result.
The lens, sensor and jpeg engine need to work in harmony to produce great-looking pictures. Optical deficiencies in the lens affect every picture you take. If the jpeg engine does a poor job processing the data from the sensor, you can get images with smudged details, poor color and contrast. If the sensor has deficiencies, then everything suffers. The trick is finding a camera with good performance in all three areas.
Note that SLR and interchangeable-lens cameras have large sensors with lots of surface area, as well as the latest sensor technology. High megapixel counts in these cameras is almost always a good thing, although with a good lens and jpeg engine a 10-megapixel sensor is enough for professional quality.
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