See manual. Set to the HIGHEST RESOLUTION your camera can support. Probably over 4000x3000.
Your camera supports different ratios like 6x4 or 16x9. 6x4 is the standard PRINT size, but 16x9 fits an HDTV perfectly so is better for viewing on a screen.
more information: http
/www.photographyblog.com/reviews/sony_cybershot_dsc_h55_review/