What You Should Know about Pixels and Using Your Digital Photos as Screen Images
Although resolution has a dramatic effect on the quality of printed digital photos, it’s irrelevant to the quality of pictures viewed on a monitor, a television, or another screen device. The number of pixels controls only the size at which the picture appears.
A bit of background to help you understand this issue: Like digital cameras, computer monitors (and other display devices) create everything you see on the screen out of pixels. When you display a digital photo, the monitor simply uses one screen pixel to display one image pixel.
For example, the image below shows a screen capture taken from a 24-inch monitor that is used for a Windows computer. Windows enables you to adjust the resolution of the monitor (as does the Mac operating system), with each setting resulting in a different number of screen pixels. Usually, you get the best display when using the monitor’s native (default) resolution, which on this monitor, is 1920 x 1200 pixels.
After setting the monitor to that resolution, you can use the Windows display-customization options to place a 1536 x 960-pixel photo in the center of the display. The picture consumes just that number of screen pixels, with the remaining screen area occupied by the various Windows desktop icons and the plain blue background that was chosen as the desktop background.
Of course, for most onscreen uses, you don’t want the picture to take up the entire display area or even as much screen space as shown in the ample. When you share pictures on Facebook, for example, post them in an online gallery, or include them in a presentation, you need to leave ample screen space for text and other page elements.
The upshot is that you need far fewer pixels for images destined for screen display purposes than you do to produce large prints. Which begs the question: What do you do if you want to be able to print your pictures and share them online or use them for other screen purposes? Always set the camera resolution to match the print size you have in mind.
You can’t add pixels later successfully to achieve a good print. You can, however, dump pixels from a high-resolution original to create a copy that’s appropriately sized for the screen. Your camera may offer a built-in tool that creates a low-resolution copy; if it doesn’t, you can get the job done in any photo editing program.