fluctuating brightness E7440

The screen brightness fluctuates up or down depending on if the content is lighter or darker. For example changing from a white background window e.g. an office document to a dark UI such as Spotify results in the brightness ratcheting downwards several times in succession, flickering with about 0.5s for each change. Going back to the bright window results in the brightness ratcheting up in steps about 0.5s apart.

It started happening after updating system drivers recently, after doing a factory re-install. At first I thought there was something wrong with my eyes! I noticed this most while running on battery with the brightness turned down in a darkened room. The effect is absolutely awful! Im guessing this is some sort of new dynamic brightness scheme to trick up the LCD contrast specs. Please tell me how to turn it OFF, because it is so visually intrusive I cannot tolerate it! I want my backlight level to stay where I set it.