"3D is a waste of a perfectly good dimension" - Roger Ebert (quoted by Mark Kermode)
A technique of film making that enhances the illusion of depth within the film. It is achieved by recording the film images from two perspectives, or by artificially applying the effect in post production with computer imagery, and replaying the images through specialised movie projectors. It also requires the viewer to wear special eyewear.
In Dr K's opinion it is a (mostly) unnecessary gimmick, that induces headaches and causes a 30% light loss.
Films which Mark admits have been improved by the use of 3D include Gravity and Hugo. Indeed, at the very start of the new 3D era, Mark advocated that films made in 3D should be seen in 3D - notable examples included Bolt ("if you see Bolt, the way to see it is in 3D"); Monsters Versus Aliens; Meet The Robinsons and Journey To The Center Of The Earth. In fact, Meet The Robinsons featured this famously chippy exchange:
MARK: Need to see it in 3D because it's not much good in 2D.
SIMON: What does that add if it's in 3D?
MARK: Well, it adds three dimensions Simon.
SIMON: But how do you enjoy it more if something pops out at you?
MARK: Because you sit there and you go, 'well, there's not a lot happening, but at least it's happening in three dimensions and they've done it quite well.'
It was the aforementioned Monsters Versus Aliens that was the point at which the tide began to turn for Mark, when numerous listener complaints began to stack up about having to pay extra for the 3D glasses: "I’ve gone from being benignly dubious about 3D to being a bit more cross about it. I’d be a lot less cross if it cost exactly the same as all the other movies". A cinema manager contacted the programme to argue that the extra cost was to pay for the technology required to show the films, but Mark was having none of it. Simon Mayo was equally appalled, saying it was comparable to paying for coffee but being charged extra for the cup with which to drink it. Despite all this, Mark still insisted Monsters Versus Aliens had to be seen in 3D though, in the same way that Earthquake had to be seen in Sensurround.
Shortly after Monsters Versus Aliens, Coraline went on release - a film Mark liked very much, but which was promoted heavily as a 3D experience - only for Mark to find he preferred the 2D version. A month or so later, Ice Age 3: Dine Of The Dawnosaurs became the film that cemented Mark's view that he was right - 3D really was just an industry plan to make more money (while pretending it was really just about preventing piracy): "It was the moment at which I finally thought, 'that's it, I'm right - this 3D thing really is for nobody's benefit but the filmmakers. There's just no reason for it to be in 3D at all'." (This meant that successive Ice Age films had been responsible for the death of narrative cinema and the proof that 3D was just a moneymaking gimmick - quite the 1-2).
Meanwhile, Hannah Montana / Miley Cyrus In The Best Of Both Worlds: Concert Tour - 3D is a better 3D concert movie than U2's 3D concert video, because U2's 3D concert video it doesn't have a bit where The Hedge throws his plectrum at the camera.
Any mention of 3D is likely to prompt Mark into pointing out that the format has been tried several times in the past - in the 50's (see House Of Wax), in the 80's (see Jaws 3) and in the 2000's (see any of James Cameron's home movies) - yet it has never shown staying power. It just seems to be one of those things that revives itself now and then, rather like Mark's anecdote about The Stewardesses.