changing DPI matters?

jchin

[FONT=Verdana, sans-serif]OK ... this might have been covered before ... however I am still a bit confused.

Given a 3000x2000 pixel image, does it matter if you change it from the default 72dpi which came straight from the camera to 300dpi in Photoshop WITHOUT changing the image resolution?

So my question is ... which image is "better"?
3000x2000 @ 72dpi or 3000x2000 @ 300dpi
In the context of sending them to an online photo printer (Costco, Walmart, Mpix, etc.).


This caused a small debate between a few members at my photography club.

Personally, I think (and I maybe wrong) ... 3000x2000 pixels is 3000x2000 pixels. The DPI does not matter. It is the resolution of the image that determines if you can print a particular size image. Right?

Please help me, once and for all, clear up this confusion. Thanks.

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pathfinder

I'm with you!

Total number of pixels does matter, as you said.

Pixels per inch ( ppi) is just record keeping, and has nothing to do with resolution.

Dots per inch ( dpi) is not used with reference to an image file. Dots per inch refers to how a printer sprays ink on paper. One pixel may be represented by 5-10 dots of ink. Technically, dots per inch does matter, but dots per inch derives from the total number of pixels and the size of the image desired.

I wrote a little tute about resolution and pixels here

jchin

Thanks. I'm glad I didn't lose it yet.