With the information in my blog post entitled Pixels (part 1) [how-many-pixels-part-1], you may conclude that 8×10 inch prints call for a 5 megapixel camera. That’s generally true, but not entirely. It is possible to use computer software to artificially increase the number of pixels. Different software programs may perform differently. The general rule of thumb is you can double the number of pixels. So, you might print very good 8×10 prints though your camera only records 3 megapixels.
Maybe you just bought a new DSLR that records images up to 15 megapixels. Those 15 megapixel images may require three times more storage than 5 megapixel images. If you shoot
some pictures on Tuesday, intended for 11×14 prints, set your camera to record large size. If you shoot some pictures on Wedensday, intended for computer screens only, set your camera to record small size.
Pixels get a little weird when you move to television display. Pixels on a computer are square. A digital image that is 400×400 pixels will display square on your computer monitor. Not so on a television screen. Television pixels (defined by either NTSC or PAL standards) are not square.
Consider an picture aspect ratio of 4:3, meaning the picture is 25% wider than it is tall. Standard television (not HD) has a 4:3 picture aspect ratio. Yet the resolution is 720×480 pixels, which numerically seems to be 50% wider than it is tall. But rest assured it is 4:3 because each television pixel is taller than it is wide. (Take a very close look at a television and you can see this is so. It is more difficult to see on a HD television.) While pixels in a computer or in your camera are equally wide as they are tall (often called square pixels), pixels in television are taller than they are wide.