by em... » Tue Feb 10, 2009 3:53 pm
You're not quite right.
The PPI of an image (resolution) should be ideally twice the DPI (screen ruling) that it will be printed at, but at the very least it should be 1.5 times the DPI.
So, if something was printed at a low newspaper quality (say 85 DPI, although I'm sure the quality is higher these days) it would need to be at least 127.5 PPI, ideally 170 PPI.
Most higher quality printing is done at 150 - 175 DPI, so 300 PPI would cover both, but if you want to go higher that's up to you - as has been said, it'll doesn't hurt to have higher resolution than you need.