It's slow with a high res scan in 16 bit mode, what I'd do is just what you did
until you've merged the two files with the layer masks, save a copy of that and
then save an 8 bit copy, which will cut the file size in half.  16 bits is
great if you have to make a lot of radical adjustments but once you've done the
main tonal and color corrections it's a good idea to move to 8 bits for files
this large.

Just bite the bullet and do what needs to be done even though it's slow.  If
you resize too small you're tossing away a lot of the advantages of medium
format.

You didn't say what kind of system you have ... my computers are a bit old now,
2.5 GHz P 4's, but I have 1.5 GB of RAM on one and 2 GB RAM on the other, set
the memory allocation much higher than the default 50% (I think 84% or so,
limiting my ability to open other large memory hog programs while PS is running
but speeding up PS), keep my (fast) hard drives defragged, set the history
state to a small number in Photoshop, 'purge all' in Photoshop often, and don't
open the File Browser when working on a big file ... my largest files are about
550 MB base (6x7 scans at 4,000 dpi in 16 bit mode) and with a couple of
adjustment layers it makes for large slow files, but with that much RAM it's
not TOO bad.

Yeah it's worth it, I'm printing some 16x22's tonight on my Epson 4000 and it's
nice to be able to do everything yourself.  Keep at it ...

Bill

Yup. Enormous is the operative term.

I take a middle road: I resize to 2400 dpi and work there. (This is my rant
that film really only supports up to 8x enlargements anyway, so 2400 dpi is
adequate. Not everyone agrees with this<g>.)

You need to keep your file size down to less than 1/2 of the physical memory
you have in your PC/Mac, since when you perform an operation, you need
memory space for both the original and the result. You need to set Photoshop
up to only save one item in its history. Of course, that means that you can
only back out the most recent operation.

Grumble: hurry up and tell that to people selling Mamiya 7s. Sigh.

David J. Littleboy
Tokyo, Japan

Photoshop Version 8 (CS) handles files of any size, any pixel dimension.
Look under the 'Large Document Format'.  Of course it helps to have 1.8gb
RAM, but it is not neccessary. I suffered through the edit of a 2.5gb file
with only 640mb RAM once. Slow, but it worked.

~~SNIP~~

Don't forget to show us some samples of your work.
Ivan

If your scanner driver gives you reasonable
control and you can reasonably perform most
of of your color corrections in the scanner
driver, then you can use 8-bit color with
impunity.

But to do this you must use those eight bits
wisely.

rafe b.
http://www.terrapinphoto.com