What is a megapixel?

Digital cameras capture images as pixel elements, known as pixels. Simply put, a megapixel is equal to one million pixels.

Digital images are made up of thousands of these tiny, tile-like picture elements. The more pixels, the higher the image resolution.

Resolution relates primarily to print size and the amount of detail an image has when viewed on a computer monitor at 100%.

Elements of picture quality

The number of megapixels is only one aspect relating to the quality of a camera, or the actual quality of a photo it is capable of producing. Factors such as camera sensor and processor, and the optical quality of a lens, play equally important roles.

Other elements determine the quality of photos and prints. They include:

§  Good lighting of a subject

§  Proper focus and exposure

§  Image clarity (lack of blur due to camera shake or incorrect shutter speed)

§  Shooting at the highest resolution and quality camera settings

Photo was taken with a 1.4 megapixel camera. The resolution is suitable for a 4x6" print. Click to enlarge.

Photo was taken with a 1.4 megapixel camera.
 The resolution is suitable for a 4x6" print. Click to enlarge.

If you buy a digital camera with too few megapixels for your printing and editing needs, resulting prints will become degraded.  A photo made into a large sized print from a camera with a low megapixel count will look fuzzy, or pixelated. So will a digital image that is cropped too much.

Viewing images at 100%

A mistake many people make it judging the quality of an image when viewing it at 100% on a computer monitor. The image rarely appears tack sharp. However, when reduced in size for displaying online or printing, a quality image more often than not looks just fine.

Determining the number of megapixels

Deciding the number of megapixels you need does not have to be confusing. Don’t let a salesperson push you to buy a digital camera simply because it has a high megapixel count.

Before purchasing, keep the following in mind:

§  the maximum print size you plan to make

§  if you do a significant amount of cropping when editing or cropping in-camera

Minimum megapixels for quality prints:**

Printed at 300 dpi

Max Print Size	Minimum MP	Resolution
4 x 6″	2 megapixels	1600 x 1200
5 x 7″	3 megapixels	2048 x 1536
8 x1 0″	5 megapixels	2560 x 1920
11 x 14″	6 megapixels	2816 x 2112
16 x 20″	8 megapixels	3264 x 2468
16 x 24″	12 megapixels	4200×2800

** Unless you buy a used digital camera, it’s near impossible to find one today with a megapixel count of under 10 megapixels.

 Source : http://www.digicamhelp.com/