Paul Kleiner wrote:But one thing I`m still not clear on--when DPI is specified, do I use that as PPI in resizing?
What I am saying is that if your image is 1512 pixels or more on the long side, you are done! It doesn't matter what the PPI says.
If your image is less than 1512 pixels on the long side, it is too small and will have to be up-sampled.
If you have resample un-checked on your resize dialog window, you can change the ppi and it will change nothing except to tell you what size the print will be at that resolution. At that point, it is a calculator. If it makes you feel better, you can put in the resolution (DPI) they asked for and it will be saved with the image but it won't really change anything as long as the resample box is unchecked. That's a good thing. They won't care if there are more pixels than they asked for, just not less. If there are more pixels than they want it will print the same.
And yes each pixel on the computer becomes a dot on the printer, so in that way they are the same thing.