Reply To: InDesign/Prepress Myths

You rarely need more than 1.5x your halftone screen frequency (assuming you're printing to a traditional halftone screen with regularly-space spots, like in a magazine or newspaper). If you're printing at 150 lpi (lines per inch) then you almost certainly do not need more than 225 ppi images. 

There's a huge difference in file size between 225 and 300, so it's useful to stay with the minimum required.

Of course, if you import a 225 ppi image and scale it up to 110%, then you have only about 200 ppi effective resolution.