When you're shopping for a digital camera, probably the first spec you'll see is how many megapixels its sensor delivers. Well what's a megapixel anyway, and how many do you need to take good quality photos?
What's a Megapixel?
A megapixel is one million pixels (short for picture element), the tiny colored dots that make up an image. And today, it's pretty obvious that camera makers are under the influence of "megapixel madness." Every new model boasts more megapixels than the last. There are now 6-, 7- and 10-megapixel compacts as well as 10-megapixel digital SLRs (single-lens reflex).
Pixels Are Like Horsepower
Like a car's horsepower rating, which equates to quicker acceleration and a higher top speed, more megapixels in a camera mean higher resolution, a term that defines detail sharpness and image quality. That said, an 8-megapixel (MP) camera does not deliver twice the image quality of a 4MP model. In order to double the image quality of a 4MP camera, you would need a 16MP (4x4) camera.
Of course, you don't need to double the image quality to see a difference when making a big print: if you closely examine 16x20-inch portraits made from 6MP and 10MP cameras, the 10MP print would show more detail.
For Pros Only
Pro photographers require this level of performance, but when was the last time you made a 16x20-inch print? For most people, 8x10 or 8x12 is the largest print they'll ever make. The only other reason having "extra megapixels in reserve" might be useful is when you crop an image and then make a large print of just that section.
Then there is the psychological factor: the idea of being able to make a poster-size print is very appealing. Megapixels alone do not determine picture quality—your camera's image-processing firmware and software, and the quality of the lens, are also important.
How Many Is Enough?
So, how many megapixels do you need? In practice, a quality 4MP or 5MP camera delivers excellent 8x10-inch enlargements; a 6MP camera turns out super 11x14 prints, and images shot with a 10MP model can be enlarged to a fabulous 13x19 inches.
If you're a bit less demanding, you can go up one print size at each MP level. But if all you're going to make is 4x6 prints and e-mail images, none of this really matters. In fact, if you don't want to blow out your buddy's e-mail, you'd better reduce the file size before sending those great shots you took with your shiny, new 6-, 7-, 8-, or 10-megapixel marvel!