Megapixel Mania!

In recent years there has been a push in the digital camera industry to put ever increasing megapixels into cameras. The megapixels seem to double every couple of years. One megapixel is the equivalent of one million pixels. Each pixel, which is short for picture element, contains tiny photodiodes which absorb light and colors. Most people who are new to digital photography may think that the more megapixels a camera has the better images it must produce, this is a myth.

While the number of pixels (think of tiny dots of color that make up a magazine image) does affect how much detail a digital camera can pick out, a number of factors combine to affect the resolving power of a digital camera. The quality of a cameras lense, the processor inside and the design and quality of the sensor all play integral roles in final image output.

Here's the deal with pixels. A digital cameras sensor can be thought of as a rectangular grid of squares, each square represents a pixel. A seven megapixel camera will have seven million of these tiny squares or pixels on it. Now, if we take the same size sensor and add 12 million squares onto it, what will have to happen to those squares in order to fit on the grid? They will have to decrease in size. The problem with these smaller pixels is that they cannot absorb light as well as the larger ones, a by-product of this is "digital noise". Digital noise looks like grainy specks in your pictures, more noticeable in the shadow and sky areas of pictures, compromising image quality.

If that's the case, why do most camera companies continue to put more megapixels in compact cameras then? Well one of the reasons is they know that alot of people are sold on the megapixel count of a camera, and they want to sell cameras. Some camera companies are increasing the size of the sensors they put into their compacts to lower the pixel density. Pixel Density is the number of pixels divided by the area of the sensor, a lower value means larger pixels with potentially better light absorbing ability. While this is not the only factor affecting image quality, it's at least a guideline.

A good example of a larger sensor in a compact is Panasonic's Lumix LX3, which comes with the same 10 megapixel resolution as the previous LX2, but with a larger sensor. This is in an effort to reduce noise, thereby improving image quality. You will notice all the proffessional DSLR cameras have very low pixel densities (due to the use of very large sensors), thereby improving image quality, and the ablity to handle higher pixel counts. Another way camera companies try to combat digital noise is with NR (noise reduction) built into their processors, an attempt to try and smooth out and eliminate the noise created by all the megapixels, kind of ironic! NR can do a decent job at this, but there will be some loss of detail in the process.

So then, the digital noise or the smearing of fine detail from overzealous NR can both affect image quality. It's worth noting that at smaller print sizes such as 4x6 and 5x7 these effects should not be too noticeable. But in lower light conditions, or any situation where the camera may need to boost it's ISO (sensor sensitivity to light), noise can increase dramatically, although noise will be much more apparent in the shadow areas of your pics. Actually, some may not mind the graininess generated from a noisy sensor, such as street photographers who may enjoy the gritty "film grain" look to their pics, especially in black and white.

Since NR diminishes detail, a balance of detail and noise must be reached, camera companies use NR to varying degrees, some appreciating detail with a bit of noise, and others smoothing out the images, it's a matter of personal preference. Two areas where more pixel resolution becomes benificial would be if you are printing large format images 11x14 and up, or if you do heavy cropping in the post processing of your images, as you crop and cut away parts of your image you loose resolution.

This is a complex issue and I would like to keep my articles easy to understand and relevant to the novice. Every camera manufacturer employs different technologies and techniques in their sensors, and takes it's own approach to digital noise and NR in thier processors. For example, Fuji is leading the way in sensor design in compacts, with an imaging sensor that has photosites capable of handling light better than most on the market, the Super-CCD.

I would recommend browsing some of the better digital camera review sites on the internet. One of my favorites is dpreview.com, in depth reviews of digital cameras, digital noise comparisons of various cameras and sample images. The purpose of this article was to make people aware that megapixel count is one of many important factors that will affect image quality, and quite often not the most important one.

Please look into the total feature set of a camera, not just it's pixel count!