Changing dpi and ppi in Photoshop

[baruke]

Hello,

I have some PS documents that were created at 600ppi. They contain flattened watercolor clip art that was originally scanned onto my computer at 600 dpi as well.

I have been using 600 dpi in order to make my documents ( soon to be wedding invitations) print ready and high quality. 

I am now learning that the 3rd parry editing app I need to use to sell my invitations only allows png uploads and recommends they be in 300ppi so the customers won't have to open large files. 

Is there any way to change the clip art that was scanned at 600dpi and brought into photoshop, into 300dpi png files without losing quality? In general, is it better to print at 300 dpi or 600dpi?

just to clarify:

-art was scanned to computer at 600ppi/dpi

-I turned the art into floral clip art and then made into arrangements on a 600ppi document

-I now need to take those arrangements I made, flatten them in PS, and somehow save them as 300ppi/dpi png files 

thanks!

[D Fosse · Accepted solution]

Open the Image Size dialog, make sure the "resample" box is unchecked (important!) and change the ppi to 300. This does not change the file in any way. It's exactly the same, as long as it has the same number of pixels. Only some metadata changes, instructing the printer to print the file at a larger size.

Ppi doesn't mean anything on its own. It's a relationship, not a thing. This becomes much easier to understand if you just look at the words and read them literally: pixels per inch. That's exactly what it means - it's all in those three words. Just a standard equation. It explains itself.

The file is just pixels. It doesn't have a size, until you give it one by assigning a ppi number to it.

[baruke]

Thanks I'll try that! So that won't decrease the quality for print?

[mglush]

Yes, that's correct. If you uncheck "Resample," Photoshop will not throw away any of your pixel data. It just reapportions the number of pixels per inch it in the document. The quality should not degrade or decrease.

Michelle