Night Vision - Apologies Mods, thread creep.
Juan T- That is a simple half-way house measure to help your eyes adjust from bright to dim light. The theory is that should a landing accident or incident occur and you have to evacuate the aeroplane you will have a better chance of survival as your eyes will already be part adapted to the dark.
Agree - only if you allow at least 20 minutes will your eyes (the rods or cones I forget which) fully adjust, red lighting was supposed to assist adapting. This does not take into account the individual overhead spotlight however.
I do agree however it's better than nothing.