For years, iPod tinkerers have known that holding down the correct two sequences of buttons (currently, hold Menu plus central Action button, then Reverse plus Action button) would reset an iPod and then bring up a hidden diagnostic mode. Various tests, including hard disk, screen, and Wheel diagnostics would appear, and the iPod could even be forced into a slave-like disk mode from this menu system.Source: iPodLounge
The color LCD on the iPod photo (re-branded name) is by default set to a brightness value of 128. It can go up to 255, which is very bright. Sure you would kill battery life it you left it at 255, and that is probably why you cannot leave it at 255. After all, the default setting of 128 is bright enough.
