When I purchased my first digital camera many years ago, entry-level models offered only two and three megapixel (MP) resolutions. The consensus at the time was that two MP were sufficient to print 4×6” pictures, and three MP were good enough for larger prints, up to 8×10.”
Two years later, five megapixels was considered a minimum, allowing some flexibility in cropping pictures before printing them or displaying them on the web.
Now, compact digital cameras with 10 and 12 megapixels are common, even higher for some advanced compact cameras with larger sensors.
The size of most digital cameras has remained compact during this time. Their overall size has not increased, and often decreased. But the sensors behind the lenses found in many consumer digital cameras have stayed about the same size.
Increased digital camera resolution and small sensors
Increased resolution with sensors of comparable size means that each pixel on a current sensor is smaller than on older sensors. If the sensor area is the same, a five MP camera has pixels that are 60 percent larger (in area) than an eight MP camera. This variation in pixel size can have dramatic effects on pictures.
All things being equal, smaller pixels mean more noise in pictures, and the relation is a direct one. Since the resolving power of a lens is not unlimited and is often relatively low for digicam lenses, higher sensor resolution doesn’t always translate into sharper images.
The vast majority of consumer digital camera still have small 1/2.33″ (6.08 x 4.5 6mm) sensors. But increasing numbers of compacts have larger sensors, 1/1.7″ (7.44 x 5.58 mm) and 1″ (13.2 x 8.8 mm). The larger the sensor, the better the low light performance of a camera, but it also can mean a larger, more costly camera.
Thankfully, in-camera noise reduction processing has improved tremendously during the years. So a current 10 MP sensor might not look noisier than a sensor with less megapixels.