I have received a request to demonstrate what is the difference between an original image file and a smaller file.
The following images are the same picture, only one is sized to roughly the size I use for my Picasa slide shows, and the other is the original size.
Click on each picture, to see the difference. The original size is the quality that I use to print my images. Panoramas are even larger, so their print quality is even greater than a single file.