Window shades up, tables stowed, seat in upright positions and why the cabin crew dim the lights during take off, these are things passengers often take for granted. Didn't know though that all these are for safety purposes? When a flight attendant tells you to put your seat in an upright position, put up your window shades, and to stow your tables all during take off, please do obey as not following them can be fatal, if not to you, it may be to the passenger beside you.
If a lifeguard in a beach tells you not to swim more than 20 feet away from the shore because there are sharks, will you still go beyond 20 feet from the shore even if you are an olympic swimmer? Same thing goes when you fly in an aircraft. Just like lifeguards, your flight attendants are your safety professionals and they know all the emergency procedures by heart, so if they instruct you to do somethings, please follow them.
Anyway, Captain Joe now explains why the cabin lights are dimmed and why flight attendants asks you to put your window shades, your seats in upright position, and to stow your seat tables in a video below. Please do watch from beginning to end.