Quote Originally Posted by JDF View Post
What the difference with push/pull.
Push and pull change the contrast rate. The effect will normally be visible in a print in the amount of detail that prints and the "snap" of the print.

Changing the rating changes the placement of your subjects in relation to the film curve but that change is not necessarily visible in the print. For example I can easily shoot Delta 400 at ratings from 50 to 1000 and make prints that are nearly indistinguishable across that whole range.