However, for color photographic quality images, higher ranges are required and are usually in the millions of colors. Now keep in mind, each pixel can then be one of either a million colors or 256 colors depending on the range. Therefore, the file must remember the location of each pixel, but also the range of possible colors for each pixel. As you can see, large, complex pictures can lead to large files. The last factor to be mentioned is resolution.
Monitors display images in square pixels and scanners scan in square pixels.
Keep the resolution setting low. To get the best-scanned image and keep the file size small, use a resolution setting that does not exceed the capability of the printer or monitor. To use any type of image for display on a computer monitor, save the image with a resolution setting of 75 or 100. This format's range of colors is 256 or less. Hence, the main use of this format is for simple graphics such as clip art and not too complex pictures.