The Doctor is taking pictures of the spinning disk-thing, Clara is standing there holding a candelabra with three candles, and Emma is staring through the doorway behind them as images of the pocket-universe start showing. Clara finally sees what Emma is looking at, and when she says, "Doctor!" there are only two candles in the candelabra. When Emma faints and we see Clara again, the missing candle is back.
When Emma Grayling opens a door between the universes, the blue wire of the thought amplifier keep moving from the front to the back of her shoulder.
On the first viewing of the ghost, The professor is taking multiple quick photographs using a Nikon F camera and a small electronic flash unit which are both correct for the time, but the electronic flash recharges in under a second each shot.
Such units at the time took between eight and 12 seconds to recharge for each subsequent photograph.
Such units at the time took between eight and 12 seconds to recharge for each subsequent photograph.
Matt Smith mispronounces the name of the planet Metebelis III, even though in his Third incarnation he spent a great deal of time trying to reach it. (it's Meh-tuh-BEE-lis, not Meh-TEB-uh-lis)
Near the beginning when the characters are looking at the board of ghost photos, The Doctor is holding a candlestick. When he goes to the table and sets the candle down, a splash of hot wax falls off and presumably lands on The Doctor's hand, as Matt Smith visibly flinches a second later.