The ideal image resolution for an 8x10 print is 300PPI, so the pixel count (size) of that image is 2400x3000 pixels which translates to 7.2 megapixels. With very large prints the PPI resolution can be lowered because big prints are viewed from a greater distance than small ones. The absolute minimum image resolution of larger prints in the realm you suggested is 180PPI and excellent print quality will be obtained at 240PPI.

So lets take a little more modest standard size of 16x20 inches at 240PPI for best quality, and that would require a digital camera with an 18.4 megapixel output. Lowering the image resolution to 180PPI at 18.4 megapixels the print size would increase to 21.3x26.6 inches.

The usual method to obtain larger prints and maintain image quality is to re-process the image file using interpolation. This can be done successfully with Photoshop to about half again the image size, and using a special algorithm for interpolation like Genuine Fractals very good quality can be maintained at 2X and somewhat larger.

Mahalo for your help...again. I am borrowing a book from a friend tomorrow
if it is not what I need then I will be utilizing your book a a resource. Thanks.
Yeah 16x20 is probably a more realistic size once matted and framed, but I do have a few that I might want to go bigger on.
As for Photoshop and Genuine Fractals...whoooo... gotta get the hardware before the software : ) Are both of those suitable on a mac?
Does the GF program provide the same results with color and B/W...does it produce greater results with one over the other?

One thing you can do is size the file as large as you want and do an 8x10 crop to have printed as a test. That way you can test the various resizing programs to see which works best. Each image should be evaluated independently as you'll see that Genuine Fractals might work better on some images and Photoshop's resizing on others. I suggest getting the trial version of GF and test it before making a purchase. For myself personally, I've never felt the need to use it, relying on Photoshop to resize.

Quote:
16x20 is probably a more realistic size once matted and framed, but I do have a few that I might want to go bigger on.
As for Photoshop and Genuine Fractals...whoooo... gotta get the hardware before the software : ) Are both of those suitable on a mac?
Does the GF program provide the same results with color and B/W...does it produce greater results with one over the other?

Yes, if you are an Apple Mac user Photoshop is available, (I use Macs myself) and I would recommend Adobe Photoshop Elements 6.0 for most enthusiasts and it's $89 I believe or close to that. Genuine Fractals is a plugin accessory that's added to Photoshop, but first try Elements Resizing to increase image file size for printing, as it may be all you need. I have never seen any difference in image results between a grayscale (B&W) and a RGB color file resized by any method to make a larger print.