Exactly what is the point of dimming the cabin lights for night takeoff and landings? The folly of this policy was demonstrated when the report said visibility in the cabin was poor because the lights were dim. It certainly has nothing to do with preserving night vision for any night emergency evacuation since any pin point of bright lighting such as that used with individual seat reading lights on, destroys night vision instantly.
The FA's don't go up and down the cabin telling people to switch off their reading lights do they?. In an airliner you can bet the galley lights will be left on for takeoff and landing so that destroys the night vision of the nearest FA.
It is supposed to be good sense to count the number of seats ahead or behind you to the nearest exit. With a dimmed cabin that is difficult particularly for those passengers that need glasses even in bright light.
The pilots will have no night vision since that is already shot by bright runway and taxyway lights and landing lights. Normally, emergency lighting illuminates escape slides so that destroys night vision before you even go down the slide. So night vision as an excuse for dimming of cabin lights for emergency evacuation simply does not add up.
Far better to have cabin lights on bright to for takeoff and landings at night. At least the nearest emergency exits can be easily seen at leisure a long way off right up to the moment to power being cut (for whatever reason). Full night vision adaption takes at least 20 minutes . As time goes by, however, we gradually become able to detect a room's contents. This phenomenon is known as "dark adaptation," and it typically takes between 20 and 30 minutes to reach its maximum, depending on the intensity of light exposure in the previous surroundings.
It used to be policy for cabin lights to be dimmed so that passengers could enjoy the view of city lights. Well that was the usual reason given over the PA. It was never about night vision.
If night vision adaption is the official reason for dimming cabin lights then why not have total darkness in the cabin for quicker night adaption . Clearly that would not appeal to frightened passengers. Far better to consign night vision adaption to an Old Wives Tale and have cabin lights on Bright so passengers can read their briefing cards up to the last minute and see where things are including nearest exits. FA's can also see if any panicky passenger is standing up prematurely.