When I purchased my first digital camera several years ago, entry-level models offered 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.

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 man compact 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. As an aside, more resolution means fewer images can be saved on one memory card.

Improved noise reduction processing

The good thing for digital camera users is that in-camera noise reduction processing has improved tremendously during the last few years. So a current 10 MP sensor might not look noisier than an “old” five MP sensor.

But many users dream for five or six MP compact digital cameras with current noise reduction processing. Such cameras would produce overall better images with less noise, particularly when using high ISO numbers.

Why more megapixels?

So why are we getting digital cameras with higher and higher pixel count? In short, because numbers sell. People compare a car’s horsepower, DVD-ROM drive’s speed, the resolution of High Definition television…and megapixels.

Most casual photographers do not need a resolution higher than five or six megapixels. Higher values do not improve the quality of pictures, and often do the opposite.

Hopefully manufacturers will stop the so-called megapixel race soon.