Pixels and Resolution

Examples showing the loss of resolution as fewer and fewer pixels are used to represent an image.
The leftmost image corresponds to a scan at 75 dots per inch of an image 2 inches wide.
 

scanned image 150 pixels wide displayed at 150 screen pixels wide	scanned image 75 pixels wide displayed at 150 screen pixels wide	scanned image 38 pixels wide displayed at 150 screen pixels wide	scanned image 19 pixels wide displayed at 150 screen pixels wide