The Megapixel Myth

Text and photos by Jon Hill, July 2004
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In recent months, the authors of the more well-known digital photography sites like Digital Photography Review, The Luminous Landscape, and Steve's Digicams have been saying more and more about the quality of pixels as opposed to the number of megapixels in a camera. They are addressing a myth that the camera makers are doing little to correct and much to encourage. This is important information when choosing a camera, so I'm going to do my part to dispel the myth as well.

Photo at right: A full size crop from a 2.7 megapixel image. Scaled-down full image below.


With the recent introduction of 8 megapixel digicams by Sony, Nikon, Canon, Minolta, and Olympus, it's clear that none of the major digicam players want to be left behind in megapixel race. They also want to continue selling you a new digicam every year or two, trying to convince you that your current model is not up to task of taking quality pictures. With those goals in mind, the manufacturers continue to push their high megapixel models on a public that largely doesn't need them and, frankly, will find the huge files generated harder to work with.

A megapixel is about 1,000,000 dots in a picture. These dots make the picture and it's logical to think that the more dots you have, the more detail the picture will contain. This is true up to a point. The problem is that before too long, other factors begin to limit picture quality. Sometimes the lens in front of the sensor (CCD or CMOS) is not sharp enough to produce the detail that the sensor can collect. So you get 8 million blurry pixels. The other problem is that as the manufacturers cram more pixels or, more properly, more "photosites" on the sensor, each photosite must ge smaller than before. The smaller the photosite, the less light it can collect. The less light it can collect, the less sure it can be about the intensity of the light hitting it. So you start getting photosites that "disagree" with each other about the light coming in and the result is some are too dark and some are too light. The result is a picture that looks grainy or has out of place colored spots or blotches in it. This is called "noise", and it is a problem with high megapixel, small sensor cameras.

Crops from a tiny 2.1 megapixel CCD (left) and from a larger 2.7 megapixel
CCD (right). The difference in megapixel count is not enough to explain the
difference in quality. We must also look at lens quality and sensor size.
These factors influence sharpness and noise levels.

So what does this mean to you, the consumer? It means you should be more interested in lens quality and actual sensor size than in megapixels. 2-3 megapixels is enough for a photo-quality 8x10 inch print. Unless you plan to print larger sizes, there's no need to have a larger megapixel count. And there are good reasons not to! The more megapixels you have, the larger your files will be. That means your memory cards will hold fewer photos and your computer will take longer when moving those pictures around or editing them.

Note: You may have noticed the prices of so-called DSLRs dropping to the $1000 USD mark in the last year. This is good news because DSLRs let you choose the best lens you can afford and they have much larger sensors than digicams. They produce better pictures for exactly these reasons. Do you need one? Probably not. However, they do offer other advantages that you might find useful, including improved shutter-lag, overall speed increase, and better creative control. The downside is that they are still expensive when you factor in lenses and they are more cumbersome to carry. These characteristics will appeal much more to pros than to snapshooters.

Finding out the sensor size of a camera isn't always easy, but you can get started learning about sensor sizes on this site. Guidelines for lenses are a little easier. Go for faster lenses, indicated by lower f-stop numbers. A lens with maximum aperture of F2.0 is generally better that F2.8 or F3.5. Optical zoom is also important. Higher values like 8x to 12x means you can zoom closer to your subject, but please realize that you are more prone to camera shake and blurred images with extreme zoom. Sometimes it's better to get a camera with less zoom and just try to get close to your subject. If you must have extreme zoom, try to get a camera with Image Stabilization, aka Vibration Reduction, aka SteadyShot, aka Anti-Shake. These technologies help you get sharper pictures of still subjects at low shutter speeds often the result of zooming in. Ignore any claims about digital zoom. It's a generally worthless feature.

Above all, read some reviews before you buy. Don't trust the hype and advertising of the manufacturers or resellers. Chances are, the digicam you already have already does what you need it to. And if you do upgrade, find a kid to give your old camera to and get ready to be wowed by their enthusiasm and creativity.



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