The Tiger 1, like other German tanks, had internal lighting powered from the tank's batteries. This is a detail from a photograph in the Turret Manual [1, see Plate 33] . It shows a lamp on the turret roof.
These "dimmer lights" ("Abblendleuchte") were a standard component used in all Panzers.
Each crew member in the Tiger's turret had a lamp. This diagram shows the underside of the turret roof in the first kind of turret (i.e. with drum cupola). The lamps were moved slightly later, when the loader's periscope and then the larger cupola were introduced, but they always had these approximate positions.
When a lamp's cover was partly open, the light would shine to one side only. Notice that the commander's lamp shines backwards onto whatever he is reading, while the other two lamps shine forward onto the tank's equipment. The wiring diagram refers to the commander's lamp as a "Reading lamp".
[2] Survey of Tiger 250122, at Bovington museum, by David Byrden
[3] Survey of vehicle 251114, at Saumur, by Jean-Charles Breucque