I am in the process of creating a slide show to be run on a TV.  The images I intend to use are a mishmash of photos taken with different cameras with a mega Pixel range of 3 to 10.  In addition there are scanned images with a resolution of 200 to 1200.  My question is, to keep the final file size down to a manageable one, what would be the optimal size for the images so as to not too great a variance in the quality in the movie?