Resolution - How much is enough?

I often hear people say that bigger is better when it comes to pixels in an image. This is not always true, but smaller is not always better either. What is best? Using enough information to produce the output desired, a web image, an 8x10 print or a 20x30 poster.

The image above (my wife on the beach in Iceland) was targeted for the web. It has a pixel dimension of 500 pixels x 375 pixels; the image on the screen is approximately 5 inches x 3.75 inches (depending on your screen resolution). I would say that it has adequate resolution for use on this blog application.

This image is the same image with the pixel dimensions reduced to 125 pixels x 93.75 pixels; the output size on the screen remains at 5 inches x 3.75 inches (remember the actual size varies with your screen resolution). Most would call this image pixelated. When the pixel size causes the image to appear "blocky" or out of focus, the pixels are too big. They are apparent o the naked eye. To have "smooth" looking images, the pixels must be smaller. The measure of large or small pixels in an image is usually determined by the number of pixels that will fit along a linear inch or pixels per inch (ppi).

More tomorrow on matching pixel s to your desired output.