.

For screen, the only important thing is the number of pixels. A laptop screen will usually have a higher DPI than a desktop display but about the same dimension in pixels.

No need to go beyond 254dpi imo for photo images. For graphic images (vector plots and the like), you need to print as high a resolution as your printer supports but to be honest, 600dpi works for me. As for sharing online, 72dpi is standard screen size that most folk have but I really wouldn't go by dpi. an image that's no wider then 1200px or higher then 800px will be fine for online sharing.

For web usage, 72 dpi seems to be the tradition. As for resolution, there's no correct answer because it's highly situational, just don't forget to not go wild because many people are still browsing within a 1024x768 desktop.

For common print usage, 300 dpi is the usual thing, from what I heard.

I always stick with 300 dpi for print and 72 dpi for web images.

if i understand it well the dpi are only a indication for the printers and they do not change nothing in the real quality of the image
But raising them do not cause any file size increase so you may just change you preference to 900 or even 1200, ..would be no any visible shift in quality (neither in file size or time needed to save ) but will be easier to print

PS
note i was thinking maybe too much to my workflow , imainly use png when i want best quality, and a good png may reasonabily
support 1200 dpi

..but in case of lossy format a highly compressed jpg saved as 1200 dpi would make no much sense , and would look no better then if saved at 70

I agree that 72dpi is fine for most displays but I would suggest that 300dpi is the minimum target size for printing and I personally prefer 600dpi for printing 8"x10"s, higher if the target is large, like a poster size print.

.... I think you meant "lower if the target is large"....

Cause when I do posters I tend to work at < 200dpi, sometimes as low as 90 for real large images. It all depends on the expected viewing distance.

http://www.sciencecore.columbia.edu/dem ... /6266.html

So from 10 feet away, the smallest the human eye can perceive is around 0.012", corresponding to a resolution of 83 DPI.

Of course this ignores all sorts of things like moireing effects, and such.

-Rob A.

yes RobA mine was bad syntax but you guessed right