Many people have their displays set at 640 pixels wide.
Many people access the site through a low-bandwidth modem.
This is obviously not suitable for full page scans, although it may be desirable for certain small images. Here is a series of thumbnails and raw full-page scans. We could image-process the scans to make the images nicer. You may have to click outside of the previous bounding-box in order to set the new region. Resize the screen to see the effect.