No worries.
Its one of those things that on paper does look really complex, but in practice is just simple maths....A*B = C...or any combination thereof.
Just create a new document, 300 x 300px and with a resolution of 300 ppi (dpi as PS likes to call it).
Fill it with something like an image or whatever.
VIEW @ 100%.
Then go to Image > Image Size... UNCHECK "resample"
Change the "Width" and "Height" values to read in Inches.....they should both be 1. (300 pixels per inch, image is 300px wide therefore it would print a 1" square)
Change the "Resolution" to something ridiculous like 1000
Note the "Width" and "Height" size will change dramatically. (In inches)
Click OK out of it and check your image.......any different? (It shouldn't be)
Now check the "Print Size..."
View > Print Size...
The image should be very small because of the higher ppi.
Change the ppi back to 300 and then View > Print Size again....the image should now be much bigger.
Note that in both cases the amount of pixels has not changed.....its still 300x300px...but the Output (Or Print Size) changes significantly.
That example demonstrates you can change the output size using the ppi......and constant pixel dimensions.
You can also keep the ppi constant and have the amount of pixels change.......check "re-sample" and you'll see.
Regards.
MrTom.
