One marketing ploy that most consumers have almost universally bought into is that the more megapixels a digital camera has, the better it is. This is one of the biggest misconceptions in the entire consumer electronics industry, possibly second only to the belief that a $140 Monster cable will make your audio signal sound better than a $12 cable (or a coat hanger). The first thing out of someone’s mouth when you show them a new camera is often “How many megapixels is it?” More megapixels not only don’t make for a better camera than one with less MP, but it may actually make it worse. Before anyone starts shopping for cameras this holiday season, I want to make sure everyone’s aware of the Megapixel Myth.

A huge factor in the quality of digital photos is the quality and size of the digital sensor inside the camera and how much light it is able to absorb. You’ve all seen grainy, noisy digital photos, especially in darker shots — that’s the sign of a sensor struggling to take in enough light to expose the photo. The sensor is a rectangular device that is divided into a pixel grid — if you have a 4 MP camera, then you’ve got about 4 million individual photo-sensitive cells on that sensor. If you then cram 8 MP onto that same sensor, with the same physical dimensions, then more of the surface is divisions, or “walls”, than light-gathering pixels. Think of it like an ice cube tray. If you have a tray that normally has 20 cubes, and then subdivide it so it can handle 40 smaller cubes, your total volume of water drops because of the extra space that the divider walls take up.

Sensors in the typical compact consumer camera can only get so big and still fit in the case. So all other things being equal — same physical sensor size, same sensitivity, etc — a lower megapixel camera will perform better in low-light situations where every possible photon of light must be absorbed. DSLR cameras have much larger sensor sizes, and so have much larger photo-sensitive cells. This is one reason why a DSLR will always outperform a point-and-shoot that has the same MP rating — the photo cells are bigger, they can absorb more light, which means less noise in low-light situations and faster shutter speeds across the board.

Now of course as technology improves, sensors get better and better at absorbing light from small photo cells, so a lower MP camera is not automatically better or more sensitive to light. But the important point here is that higher MP does not mean you’re going to get a better image.