In the latest issue of PC Authority, on sale now at your local newsagency, is a complete guide to understanding camera technologies, including the following advice about a common marketing tool - megapixels:
One of the biggest benefits, and often misunderstood, aspects of upgrading from a cheap point and shoot digital camera is better image quality.
If you want to take the sort of photos you see in photo competitions, or that are good enough for a wedding album or to blow up and hang on your wall, then a DSLR or some of the other better quality cameras available will help you achieve things that are more difficult using a compact.
With many cameras offering at least 12MP, most people have more than enough resolution (unless you're shooting professionally) - the game has moved on.
Megapixel-count determines resolution, but it tells you nothing about the quality of the resolution. More megapixels means the picture can be viewed or printed with greater detail at larger sizes. It won't tell you anything about the exposure, sharpness, colours, and introduction of noise.
More important is the size of the sensor and something called "pixel pitch". Cramming more megapixels into a smaller sensor means smaller pixels and the sensor won't be as sensitive at low light levels. Increase the sizes of the sensor, the theory goes, and you provide more room for larger photoreceptive pixels, which translates into more light sensitivity and less noise when shooting at higher ISOs.
Canon EOS 1000D: The image sensor on even a budget DSLRlike this is much larger ( 22.2 x 14.8 mm) than most powerzoom fixed lens cameras - like the similarly-priced Canon PowerShot SX1 IS (1/2.3 inch)
A DSLR like the Canon EOS 1000D and a power zoom like the Canon PowerShot SX1 IS mightn't be drastically different in size or price, but inside the 1000D is a bigger APS-C sensor compared with the 1 / 2.3in sensor in the SX 1. This mightn't necessarily matter when shooting in sunny daylight, but when you go indoors, the light sensitivity and ISO capabilities of the DSLR will open up more creative options.
There is a trick used to combat noise on cameras with smaller sensors. It's called noise reduction, but the tradeoff is reduced image detail, which can be noticeable as smearing or blurring of the image. Keep this in mind when you see sub-$500 cameras with settings as high as ISO 3200.
Also see our Group Test of 11 Digital SLR Cameras