JDM von Weinberg , Apr 28, 2008; 06:07 p.m.
There are constant debates about this sort of thing, but changing the image to between 180 to 360 to 600 dots per inch at any given size will normally produce an more (at the upper end) or less (at the lower end) acceptable print for viewing. Much above 360-600 dpi is 'wasted' in that a 1000 dpi print will not necessarily look much better to the eye than a 600dpi. In any case, all reduction in the _quantity_ of data will necessarily lead to some loss in _quality_, so the issue is one of how much of a 'hit' in data loss can you take before the result is unacceptable to the viewer (and to you). This is what our friends in the Warsaw Pact countries used to call a "contradiction" and in this case it is not resolvable. It's for you to decide how much 'crap' you will tolerate.