Can I just toss in a few ideas here about the issue of scanning resolution and printing resolution? Nesster referred to 300dpi as printing resolution - it is true that many high quality printers will print at 300dpi, but that does not mean you scan at 300dpi. Here's why.
Let's say you want to print an 8 x 10 print; that's 8 inches by 10 inches. DPI means dots per inch, and each dot needs a pixel. To print an 8x10 at 300 dpi you need an image file that is (8x300) x (10x300) pixels or 2400 x 3000 pixels. With a 6x6 negative you'll probably print at 8 x 8 inches or 2400 x 2400 pixels image size (assuming you don't crop). OK so far?
Now, you are starting with a negative at 6x6 (cm) or 2 1/4 inches square. To turn 2.25 x 2.25 inches of negative into 2400 x 2400 pixels, you need to scan at more than 300 dpi: you need 2400 / 2.25 = 1067 dpi.
For moderate enlargements, scan at 1200 dpi - that will give you a file 2700 x 2700 pixels in size. And more importantly, this will capture a lot more fine detail from the negative compared with scanning at 300dpi. This is the reason for high-res scanning capability - to capture all the detail in the neg and to make a large file size (in pixel dimensions).
A file 2700 x 2700 pixels in dimension can print at 9 inches square at 300 dpi, with 1 pixel per dot on the paper, and no need for further interpolation by the software to produce extra pixels. If you need to print bigger, scan at any resolution up to the scanner's maximum optical resolution (ie true scanning resolution with no interpolation by the scanner software).
The file sizes will be huge, especially with colour negs and saving in TIFF format. But if you want quality that is the only way to go. I generally scan initially at 600 dpi just to give me something to look at on the screen. (600 dpi x 2.25 inches) x (600 dpi x 2.25 inches) gives me a file 1350 x 1350 pixels, which fills the screen on my monitor. That lets me see if I want to make a print, in which case I go back and take a best-quality scan, maximum resolution, maximum-bit colour saved as TIFF. Then bring that into Lightroom or Photoshop for cropping, levels etc.
So - your scanning resolution should be guided by the file dimensions you need for your purpose - for screen display or for printing.
Last edited by ChrisN; 09-21-2008 at 04:17 AM.