Cropping for DVD

I want to crop still pictures in Photoshop which will be used to make DVD video using Premiere. I want to be able to crop the pictures in a way that they have the correct proportion to fill a DVD screen. I know I could just put in the size, but I would like the additional option of cropping proportionally. Is there a way to do this? Thank you.

Just set the proportions on the option bar of the crop tool - don't set the resolution and PS won't resample.