Digital graphics are composed of small colored squares called pixels. There are many different ways of saving the pixel information on a disk, called formats. For web pages JPG and GIF formats are the most used. JPG and GIF are compressed formats that offer 40 times smaller file sizes, allowing 40 times faster loading for web pictures.

In the example we worked through in the last page, JPG created the smallest file size. This will not always be the case. Sometimes GIF will be the best choice. If changing from JPG to GIF is simply a matter of Save As and change the file type, how do you know which to use?

One hint is in the icons used by Windows to signify the different file types. Look at these icons below:

If you look closely, the JPG icon has a tiny picture of a sailboat and a sunset. The GIF image is signified by a diagram including a square, triangle, and a circle.

In general, graphics with a lot of gradations in color (say a human face) are best represented using JPG format. Diagrams with sections of the same color over continuous parts of the picture are best represented by the GIF format.

This is not always a hard and fast rule. Sometimes you need to save a graphic both ways and look to see 1) quality of the image and 2) file size of the image. There can be some difficult tradeoffs when one format is smaller that the other but not as good looking. The Ichiro pictures earlier are a GIF file from the Mariners web site, not JPG.

Remember, using Paint or another graphic program you can change the format of any picture to a different format. Choosing the "right" format will be a judgment call only you can make.