The most important numbers in your photograph regarding image resolution are the pixel length dimensions. Does that sound like gibberish, or what?

Upload an image to picnik.com, it's a simplified online version of Photoshop, and click on the edit tab and then the resize button.  You'll see the pixel dimensions of your photograph there.

The sensor in your camera has a pixel dimension.  Every photograph your camera makes is this fixed dimension.  Think of the grid as a line of single pixels along the bottom and the side of each digital file.  Multiply the two dimensions and you'll have the surface area, or the megapixel measurement of your camera.

Marketers have latched onto "megapixels" as the definition of digital camera quality; unfortunately, it is not the actual value of a digital camera. Look into features that effect the shutter lag or the speed at which the camera can write to the card, instead.  The lens quality has a huge effect on the clarity of a final image.  Many of the first digital cameras had tiny sensors, and the images produced with them are equal in quality to the skill of the photographer who made them.



DPI (Dots Per Inch) is a subject for a much longer discussion.  Don't pay attention to DPI as the guide for image quality, either.

I'll post later about the recommended dimensions required for different print sizes.