DPI vs PPI

[Jeff Mottle]

This came up in another thread so I thought I'd post it to the FAQ section of the forum:

 

DPI is often wrongly used in place of PPI. You use PPI in digital work and DPI for print work. Photoshop only lists it as DPI for some reason although they should know better. If you want to read some good articles about the difference these are pretty good:

 

http://www.tildefrugal.net/photo/dpi.php

http://www.design215.com/toolbox/print_guide.php

http://graphicdesign.about.com/libra...y/aa070998.htm

[Limbus]

This came up in another thread so I thought I'd post it to the FAQ section of the forum:

 

DPI is often wrongly used in place of PPI. You use PPI in digital work and DPI for print work. Photoshop only lists it as DPI for some reason although they should know better.

 

I think it should be clarified that DPI ist for print work with laser or inkjet printers where as offset printing uses LPI (lines per inch).

And my Photoshop also knows PPI. In the "File" -> "New" dialog and the "Image Size" dailog it says "pixels/inch".

 

Some more links:

http://en.wikipedia.org/wiki/Pixels_per_inch

http://en.wikipedia.org/wiki/Dots_per_inch

http://en.wikipedia.org/wiki/Lines_per_inch

 

Florian

[DennisB]

The bigger issue, at least in my experience, relates to confusion about working sizes. Specificially, many think of working with resolution in terms of ppi rather than image size. They never realize that what the see on their display isn't factored by ppi (other than the display's Control Panel setting anyway).

 

IMO, it's much easier to work with print resolutions if you simply multiply the size of the print by the printer resolution. For example, if your print needs to be 24" square and you're printing on an Epson 7600 inkjet with a 180 dpi print resolution, your image size (its width and height in pixels) needs to be 24*180 or 4,320 pixels square. That's all you need to know.

 

I encounter a lot of people who think a 300 ppi file is always bigger than a 72 ppi file. They often have difficulty grasping that ppi makes no difference when working on screen. It only matters when you're ready to print.

[AlekseyR]

i haven't dealt with this much, but always haer people having problems with this? I mean it's pretty straight forward, right?:

 

On your monitor you have a resolution in pixels. When you print you can decide how much pixels you want printed in each inch, which will appear as dots, hence DPI.

 

Or am i missing something?

[shaneis]

Tact.

[AlekseyR]

huh?

 

better?

[alfienoakes]

Tact.

 

:D

[shaneis]

:D

 

[ihabkal]

smiley contest?

I'm in :)

[AndyC]

i haven't dealt with this much, but always haer people having problems with this? I mean it's pretty straight forward, right?:

 

On your monitor you have a resolution in pixels. When you print you can decide how much pixels you want printed in each inch, which will appear as dots, hence DPI.

 

Or am i missing something?

 

Erm, yeah, its weird, one of those things some people cant get their head round. I still know artists tell me they are setting max to render at 300dpi. ?????