Of course it doesn't necessary for well-known types of lock, but sometimes i think picking would be much easier and convenient if i can see inside the keyway.
yesterday i make light device for locks using light cable and LED light.
light cable is slim enough to enter into the narrow keyhole and make inside of the keyhole bright enough to observe. it might be successful job but i don't think i will use this useful - i don't need this.
so this is my question : are you using light, endoscope or magnifying glass for lock? is it useful? when do you use that?