resolution dpi ppi

[tinkering]

What is the difference between dpi and ppi? I am submitting images to go to print in a community history book. I was told the images should be 1200 dpi. When I check the image size in PS it has ppi. Shouldn't 200 or 300 ppi be OK for printing? What is this 1200 they are talking about? It sounds like overkill?

If I raise the ppi from 200 to 300 it appears to make the image size smaller. Is that an OK way to raise the resolution if the reduced image size is acceptable?

[Impulsive]

DPI = Dots per Inch
PPI = Pixels per Inch

So DPI and PPI are exact same terms ^^..
And 1200 is a normal DPI/PPI rate for images ^^...

[rachjm]

If I raise the ppi from 200 to 300 it appears to make the image size smaller. Is that an OK way to raise the resolution if the reduced image size is acceptable?

It IS making the image smaller, and yes, if you're happy with the reduced size then this is ok. You're not actually adding resolution when you change this number - you're just 'redistributing' it.

To actually add resolution you need to check the box that says "Resample Image" in the Image Size dialog - there will be some quality loss if you do this, however.

[artd]

Normally, for printing purposes, you don't want to reduce the number of image pixels at all. Throwing pixels away will always result in less quality. Simply make sure the "Resample Image" box is not checked when you change the ppi setting. And yes, I'd say that a ppi setting of 1200 is definitely way too much. Generally, 300 ppi is about right for printing (it would depend on the image size and desired print size). Using 1200 ppi would result in a very small printout I'm wondering if you understood the request regarding dpi correctly. Maybe they were referring to their printer's resolution or something? Although dpi and ppi are often used interchangeably, that's not really correct; they're not the same thing. Here's a webpage that does a pretty good job of explaining the difference:

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

[Impulsive]

Wow. I was living in the conscience they were exactly the same ^^... Thanks for putting this right...

Impulsive....

[artd]

Heck, I can understand anyone thinking the two terms mean the same thing; I've read they're the same many places on the web (but it's just not true). Thanks Impulsive for not being upset when my post contradicted part of yours...I always hate it when that happens

[Impulsive]

Do I seem like a frustrated person? ^^ (* Big smile towards my sig * )

Hey, I'm here to learn to...

[Isick]

Ah I did not know the either. I was always under the impression that it mixed the colors prior to printing rather than printing each color separately within each pixel. It sounds more like a TV screen in the respect then.

Thanks for enlightening us.

[Impulsive]

Take a magnifying glass and check it yourself... Even on high resolution printers, if you magnify it enough, you could see the same sort of dot pattern as on large poster prints (with the RGB dot's...)