Much more, and you could be running into alternate problems. When you cram more pixels onto a sensor of the same size, you’re making the pixels smaller, and smaller pixels have less capacity to handle light.

Think of sensors as a field of buckets. Light is rain, and when it rains, the buckets fill up with water. Bigger buckets can handle more water before they start spilling over than smaller ones. When water spills over, you get digital noise.

The new digital SLR war is in the realm of noise, and more accurately, the cameras ability to handle noise at higher ISO sensitivities. What good is a 20 or 30 megapixel camera if the pictures you take at ISO 1000 are noisy to the point of being unusable? That’s why a large format sensor is typically a better noise handler, and why cameras will more megapixels are generally not able to contain noise as well as their lower megapixel brethern.

The camera companies kept pushing out new models, baffling an unsuspecting public. Megapixels became a household word… but the problem was, not too many people could define what a megapixel was. If they could, they most likely didn’t know the implications of it. What’s the difference between a camera with four megapixels, and one with ten? There’s got to be some difference, right? A better, higher resolution CCD means better images… no?

Having working in digital photography tech support for several years (barring a brief hiatus) I’ve come to my own appreciation and understanding of the megapixel war. In all honestly, the camera companies have passed an invisible line they don’t like to talk about. I like to call it the “six megapixel line“. Once you’re aware of it, you begin to realize that megapixels are really not a valid selling feature at this stage, and the areas of concern shift to optics, design, and features.

For most “common shooters”, six megapixels is quite enough – unless you like to print large or crop a whole lot.

A six megapixel image can be printed at 8×10 or 11×14 with the same identical clarity you would get from a ten or twenty megapixel image. In fact, I’ve seen sharp 2×3′ (foot) prints from a six megapixel image. Typically, most people will print nothing higher than 4×6″ – your standard snapshot size. Once you get into the 2×3′ range or larger, I would contend that you’re not a “common shooter” anymore… and the argument for a higher megapixel count is valid.

Most people, however, will never need that.

It’s always interesting though to talk to people who are more than willing to go out and spend more money on a feature (megapixels) they don’t truly understand or require, as New York Times technology editor David Pogue discovered in his street piece.