printing dpi revisited

[YDegroot@xxxxxxx]

This came froma w ebsite of a guy who shoots art nudes. I hope no one is 
offended.
The PhotoShop tip site is really helpful.

FROM http://photoshoptips.i-us.com/Nudes.htm

Photoshop File Resolution

Keep in mind the basic guidelines of file resolution. For web pages, the 
resolution needs to be on a 1:1 ratio with monitors, or 72 dpi. For grey 
scale halftones, the rule of thumb is: the dpi (dots per inch, 
equivalent to ppi or pixels per inch) should be twice the lpi (lines per 
inch). So if you are preparing a scan for a newspaper that prints with 
an 85 line screen, your file resolution should be about 170 dpi (at 
final size). This rule generally holds true for color separations, 
although most color houses know through experience that you don't need 
more than about 1.75 times the lpi. For 150 lpi color separations, 265 
dpi is quite adequate and anything larger is "wasted space." This is 
because there are four sets of screens overlapping (intermeshing at 
different angles) each other instead of just one set of dots for grey 
scale images. 

For a typical 300 dpi laser writer which prints only up to 53 lpi, 100 
dpi grey scale scans are adequate. For the original Epson Stylus Photo 
ink-jet printers (which image at 720 x 720 dpi), the maximum resolution 
should be 240 dpi (and, according to Epson techs, anything higher is 
re-sampled down for you by the printer's software). The newer Epson 
Stylus Photo EX, imaging at 1440 dpi, recommends files up to 360 dpi for 
optimum quality output. You may, however, be hardpressed to actually see 
the difference between a 240 dpi and a 360 dpi file printed on an EX 
unless your scan is a drum scan from a large format negative or 
transparency. For continuous tone digital imaging, the necessary 
resolution is relative to the printer's resolution.