When I'm in PSP and I go to Image/RESIZE and uncheck 'resample using..' then I change the resolution from 72 to 300. The image pixel size does not change but the resolution is upped and the print size is smaller. What is this process called and does it degrade the image in anyway? From what I can see it only changes the size of the print out.

DPI is only relevant to printing..

DPI is "dots per inch"

The higher the number, the higher quality of the print..

Hi, thanks for responding. I need to know if what I describe above degrades the image. Some sites like iStockphoto do not want you to 'rez up'. Is this considered rezzing up? And if it doesn't degrade the image, then why should it matter? I didn't think it did anything except make printing better so I can't see why it would matter unless it degrades the image.

What you're describing doesn't degrade the image. In fact not a single picture is changed. What it does is change a flag in the drawings data that's just says "1 inch of this picture will contain 300 pixels (dots) when printing". Which just means that if your photo has a resolution of 3000x2000 pixels the resulting printing size equals (3000/300 = )10" by (2000/300 =) 6.6"

What I think iStockphoto means is don't upsize your picture from 3000x2000 to 6000x4000 for example because you'll just be adding data. In other words you're creating pixels out of thin air.

Wonderful, that's what I was hoping to hear. thank you both so much.