DPI or PPI? Which to use?

[Francis S]

Hi!

I was reading about DPI/PPI, learnt about it in school... graphic design. They say DPI is only for printing. That on web we use PPI. But everyone say DPI for web design, which if i understand right doesn't make any sens since its for printing! And they say DPI for Mouses's sensibility! Is that the same thing? Why do people say DPI for other than printing, on computer, if its supposed to be only printing?

And does the dpi/ppi REALLY matter for web design? Why? In what?

I greatly appreciate any explanation!

[Duncan]

The two are often mixed up as though they are the same thing. You are right DPI = Dots Per Inch and is a count of how many dots of ink are squirted on the paper. Something printed at 1200 DPI will be a good professional print quality and 300 DPI will be a good home printer quality.

There is a lot of nonsense talked (often by teachers who should know better) about PPI (Pixels Per Inch). You cannot magically add or remove the number of pixels on a screen. You cannot have the pixels spread themselves out because you want to display an image at 10 pixels per inch. An image will look the same on a large TV screen or on a computer monitor or on a small phone screen whatever the PPI setting you used.

See...

http://www.cvillecameraclub.org/howto/ppi/

http://www.rideau-info.com/photos/mythdpi.html

http://www.lightpreserve.com/info/in041126.htm