You can burn the iPhoto Library file under Users / You / Pictures / iPhoto to a DVD.
But a DVD only holds 4.37 (4.38) GiB of data.
If you iPhoto Library is bigger, you could open the iPhoto Library file via right click > Show Package Contents and copy all the folders to another location and burn DVD by DVD.
I hope you mean data DVDs though, as for video DVDs other steps need to be taken, but a video DVD wouldn't be a backup so you obviously mean data DVDs.