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Originally Posted by GregScheidemann  They can't produce anywhere near 300 dpi with their 150 lpi screens, but you do need to submit a 300 dpi at the full size of reproduction, to avoid to possibility of moire appearing due to the 'phasing' to the two resolutions (150 dpi and 150 lpi) matching up in odd ways. |
This doesn't make much sense. 'LPI' stands for 'lines per inch', 'DPI' is 'dots per inch'. As a rule of thumb [there's some 'frictional loss' due to the differences in printing method] you can use the number '2' to convert one into the other. You may remember from geometry class that to define a line you need two dots; 150 lpi come down to 300 dpi. That's exactly where the myth of the standard 300 dpi stems from. Moiré has to do with the angles at which the different colour plates in a CMYK process are printed.
Actually many magazines do not print at 150 lpi, which is a quality found mostly in High Art mags [are there still any around?], typically you see magazine photos printed at 120 lpi, which translates to 240 dpi. In case you wonder about Adobe's default printing resolution, there you have it. As several knowledgeably people point out ever so often, 200 dpi is well enough for most subjets to be printed - even landscapes!
Many folks still think, 'the more the better', which is wrong. The only thing you achieve when throwing 300 dpi at your inkjet printer is a slower system, less available RAM for the time of printing, and the print driver throwing away all unnecessary data. Giving a high-res image file to your printing house only makes sense because they usually know much, much more than you about what they need, that is they change all parameters to the needs of their machines and processes.
Another catch is the very sophisticated concept behind modern inkjet technology. They are not printing at the file-defined relative resolution anymore [which would mean the dots are put side by side without overlap] but at their own physical
and then layered. In the case of Epson that would be 360 dpi for cheaper SOHOs and 720 dpi for high-end devices like the 2400 or 3800. The dots are then put unto each other to create smooth gradients and cover up borders and splatter.
From experience I can say that a 4 MPx camera is capable of producing photos easily printable up to A3+ [329 mm x 483 mm] without any loss or interpolation, just straight from the camera. I did and do those with an Epson 2100.
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