Earlier this year I saw an FA inform two pax (an older-looking couple, sitting together) across the aisle from me that they may not have their camera on during takeoff/landing -- this was only after a disgruntled pax (sitting behind me, he was irritated at being asked to move from his originally booked seat in their row in order to accommodate one of them, a handicapped pax) griped at the FA inflight.

I've asked FAs before when I've been seated in 15K if it was okay to take pictures of takoff/landing, and always been told it's fine. I just try to be discreet about it so other pax don't get all weird about "all items with an on/off switch must be turned off."