Resizing images and resolution question

I have been resizing some older jpeg images and have a question. The original images were saved at 72ppi. I am increasing the size and am using 96ppi in the process. However, after I go to "save for web," optimize to file size 800, and hit save the resolution of the resulting image has returned to 72ppi. Why does this happen? I cannot see anything in the "save for web" options to permit me to retain the 96ppi res.

Lots of past discussions on this, Joseph. Short answer is PPI is meaningless for digital images. Ignore it, it has no bearing on anything related to screen display. An 800 pixel image @ 72 PPI is identical to the same 800 pixel image @ 96 PPI is identical to the same 800 pixel image @ 1000000 PPI or any other PPI. All that matters is pixel resolution and, in the case of JPEG, the amount of compression. These two factors are what determine the size of the file on disk.

PPI (or DPI) only really matters when you go to print, and even then only because it's a function of how much pixel resolution your file has, and how many inches of paper you wish to enlarge it over for the print.

Thanks Royce. I now recall hearing that before but it must have been pushed out of my memory bank by some unimportant data.

It doesn't help that contests, agencies, photo clubs, galleries, publications, etc. all keep asking for digital files at such-and-such PPI or DPI, as if it means something when usually it doesn't. Unless they are making prints, I wish they would all stop talking about it. It would create less confusion.

Even in the case of publications like magazines, they probably shouldn't talk about PPI or DPI either. They should just ask for the full resolution digital file, and then take care of translating it into print resolution themselves. Most photogs don't know how to optimize a file for CMYK press printing anyway, so the publication's own photo editors, designers and techs already have to do a bunch of stuff to each submitted file before it can go to print...