I thought others might be want to hear about an interesting approach to LARGE panorama creation I ran across by accident. When I got my 4X5 transparencies back after a recent trip to death valley, I realized that I had panned from one shot to the next and there was a slight overlap (5-10%). Although the light had changed a little in the few minutes that elapsed between shots, I was able to stitch the two photos together using Panotools and PTGUI software and a curves layer to match the luminosity and colors.
To my surprise, even with this tiny bit of overlap the stitching process was nearly perfect. A family member was unable to see the seam even at 100% magnification in photoshop. This was from two 250 MB drum scans. The average distance between matching points of the two scans was only 4 pixels! I thought I could pick out the seam, but when I checked in Photoshop it turns out I had picked an area that was not on the seam. The resulting panorama has an aspect ratio of about 2.5:1. With this amount of information I could print up to 30X75 without loss of quality (but will probably stick with 24X60).
It is a little tricky learning how to use this software combo, but well worth it. PTGUI is a front end (doesn't run on Mac, though) for Panotools that makes panorama creation fairly easy. There is a Panotools group on Yahoo groups and the members are very helpful. Also, you can output each piece to a separate file which can then be put on a separate layer in photoshop, so it is easy to adjust the color matching.