Of course I know the general rule is 300 ppi or higher, but I have a few photos I took in 2005 when I was only shooting JPG on a Canon 10D that I would like to get printed into 8x10s or 8x12s(I've since graduated to a 5D and shoot only in RAW). When I open these files, they are originally sized at 11.378 x 17.067 inches at 180 ppi. When I convert them to 300 ppi, they end up sized at 10.24 x 6.827 inches. And when I size them to 8 x 12 at 300 ppi, the pixel dimensions go much higher than the original file, so obviously this might not be the best idea. So now I'm thinking of printing them at 8 x 12 at 255 ppi where the pixel dimensions remain the same as the original file. Will there be a noticeable difference? I plan to sell these in a gallery so quality is extremely important.