Correct, DPI and PPI are not the same thing, I do know the difference. I also did not say they were the same thing, I said ''whatever you might refer to it as'' But, they can so easily be transposed in general discussions of graphic images. Sort of like talking about bison and buffalo when talking about those related animals, or even dolphins and porpoise, yadda, yadda, yadda :).
All this is apparently a matter of definitions and interpretations between us. I am not wanting to debate, just to clarify my thoughts. I do not doubt your apparently through knowledge and experience. None of it is needed by husadawg to help resolve his different results for photographs from two different cameras. I was just letting him know that there is more to picture clarity and final hard copy size than simply the picture resolution alone. Hopefully some of this info, from us, can explain more than (I am sure it) does confuse.
Dots (or spots) are the smallest image element you want separately defined when scanning. Pixels (picture element) are the smallest image element you have on a display (containing the full color info for that single element) (I note that because there are some display softwares that further define sub-pixel info, such as MS ClearType, for apparently smoother image edge transitions).
DPI is a setting, and there is not a separate field for pixels in a JPG file. Dots are typically referred to with scanners, and Pixels are generally referred to when talking about images on a computer display.
You set a scanner to scan at so many dots per inch. When scanning at a larger DPI setting (more dots per inch) will result in a larger file. But when a camera takes a digital image, and stores it as a JPG, the DPI field may get set, even though it is irrelevant.
And I did not say that DPI setting was in the EXIF data. I said, after mentioning DPI, that there were other possible fields in the JPG format, like EXIF. I am sorry if you misinterpreted it as the same area.
If you look at the details for EXIF, there are possible fields for XResolution and YResolution, which, when recorded, can be used for the 'optimum' display setting. That is essentially PPI, but not exactly.
I can change the recorded DPI setting in any of my JPG files from 1 DPI to thousands-of-Dots PI, and it would not necessarily change the file size, nor my displaying resolution (this is the setting after the scanning, not for, and prior to, the scanning). It is just a setting, and my software (IrfanView, among others) can ignore it, to get the display size or print size that I want. Or I can have my printing follow the setting of the DPI to get the defined hard copy size (up to the capability of my printer).