When you say that your file was scanned at 1200 resolution do you mean 1200
dpi? If so, that is a very low resolution scan and may not result in very
high print quality. With the file opened in Photoshop you will want to look
in the image size dialog box and see how many pixels per inch (that is PPI
not dpi) your image contains at its current size. Then with the resample
box UNchecked change your long dimension to 21.1" and again look at how many
ppi that you have. If, at that length you have 240 ppi or better you
probably have sufficient quality to produce an acceptable print. If you are
close to but below that figure you can probably check the resample box and
insert a higher ppi number and up-sample your image. If you are quite a bit
below 240 up-sampling will not be a very satisfactory solution. As far as
file size is concerned 553 MB is not all that large for an uncompressed pano
file.
Chuck


Well, I have to admit that I've always been confused by the
interchangeability of terms when people refer to DPI and resolution.
I should say that when I scanned the negative, I scanned it at "1200
dpi" setting under "resolution." When I opened it up in Photoshop, as
you suggested, I find that the pixels per inch is listed as 1200.
When I change the long dimension to 21", it changes my pixels per inch
to 395.143. It sounds like my quality should be just fine if I'm
understanding your e-mail correctly because my ppi is well above 240.

My main thing was I just wasn't sure what I had to do to make sure I
had the image set up so it would print to the correct size at the lab.
I never have to do this when I print at home. I scan a negative (or
take an existing digital photograph), open it up in Photoshop, tell
Photoshop I've got 8x10 paper loaded, and then drag the picture to
whatever size I want on the paper and hit print. This whole idea of
pre-sizing a picture for the lab was sort of foreign to me. Now that
I know 553 MB is not unusual for an uncompressed pano, I won't worry
so much.