the mysteries of jpeg dpi

[jfred]

embarassing question perhaps... but here goes anyway :o

The jpeg's that come out of my 20D are listed as being 72 dpi and 3504*2336. The printers I have access to, are 600dpi resolution.

Should I be worried about adjusting dpi, or for average (6*4 or 7*5 inch) printing, should I just play around with contrast, USM etc... and then let the printer and software get on with it?

thanks in advance

[etaf]

the default DPI {PPI} is 72 aas thats the general rule for viewing on a screen.
when you change to 300PPI for a printer then you will see the max size you can print
goto imagesize and change the document size there - set it to 300PPI and then you have the max size

[tim]

Try this thread (http://photography-on-the.net/forum/showthread.php?t=61727) too.

[jfred]

thanks guys!

[Bodog]

embarassing question perhaps... but here goes anyway :o

The jpeg's that come out of my 20D are listed as being 72 dpi and 3504*2336. The printers I have access to, are 600dpi resolution.

Should I be worried about adjusting dpi, or for average (6*4 or 7*5 inch) printing, should I just play around with contrast, USM etc... and then let the printer and software get on with it?

thanks in advance
Let me clarify another issue here also. You mention your printer resolution of 600dpi. The term dpi (dots per inch, printer resolution) is unfortunately used interchangebly with the term PPI (pixels per inch, image resolution). They are not the same thing! Modern inkjets can lay down dots anywhere from 600 to 2880 dpi (dots per inch, not pixels). Think of a pixel as being a tiny square. If the image resolution is 300 ppi, then each square is 1/300 inch by 1/300 inch. Now, imagine each pixel is further broken down into tiny squares. This is the printer resolution. So if your printer resolution is 600 dpi(dots, not pixels), then each pixel can contain 4 distinct color dots at 1/600 inch each. That would be the minimum required to print a 300 ppi image. For a really detailed print of 300 ppi, you should have a 1200 dpi or higher printer.
I apologize for the long ramble here. Sometimes I have a problem expressing myself in writing, and this is a complicated, confusing subject that not many people fully understand (myself included). The point I want to make is that pixels(PPI) and dots(DPI) are not the same thing. It takes many printer dots to create one pixel.