When playing DVD's and BD's on my PS3 how do i remove the black bars at bottom and top of the TV?

I feel like i have amended the video settings 500 times to try to remove the dreaded black bars in order to watch films on full screen, has anyone managed this? Which setting combination makes this work? My PS3 is the original 60Gb (recently upgraded to 500Gb) version and I currently have Firmware 3.01 installed on the machine, not sure if any of that matters. Please help if you can. Cheers.