A question about image resolution...

and thought I'd try here, although I don't use PSP and this is a very general question.

I have photos which, when I look at the image info in Irfanview, are 72dpi (which I presume is ppi). However, when I look at the EXIF info (these are photos taken with a digital camera), I see Xres and Yres at 180 (pixels?) which suggests that the resolution is 180ppi. One image (600 x 800) has a print size showing of width 11 inches, and is fuzzy and horrible. It might have been resized or resampled at some point, I don't know. Another image is width 2480 with print size of 21 something inches and has to be at least four times as clear as the other-- probably more. Huge apparent difference. And yet both seem to work out to be 72ppi.

So, this leaves me somehow confused (well, more confused than usual). Maybe someone can clarify or point in the right direction to find out. Thans in advance,

Phil T.