"Here, one of the many delights of the early scenes set in verdant, bucolic Hobbiton is slowly realising that Frodo (Elijah Wood) and Bilbo (Ian Holm) really are half the size of Gandalf and not having a clue how Jackson has managed it. Some sort of digital chicanery, I'm sure, but who cares - it works. Magically. "
Hmmmm. Maybe I'm just weird, but I not only noticed a lot of the ways in which they did it, but they really bothered me. It was part of what killed the first part of the movie for me.
- Obvious body-doubles: every scene where they could, they used body doubles, in some cases even obviously computer generated ones. Every scene where the camera was more than 20 feet away, they seemed to cut over to body doubles. If they had looked more like the originals it would've bothered me less, but there were several scenes where it was glaringly obvious. In addition to the scenes where the camera is far off, look for scenes where you never see the face of either Gandalf or the hobbit he's with - it's almost definitely because the person with their back to the camera is a body double.
- Gandalf's cart: this was a much more clever one, but they didn't quite pull it off. If you look at Gandalf, in several scenes while riding on his cart, you're actually seeing McKellan's head and arms (and torso, perhaps, I forget) popping out of a dummy dressed to look like him. They do it fairly well, in that they don't make his head or arms seem overly small, but you can see several scenes where he moves unnaturally because, well, his legs are fake. I assume he's kneeling, with his legs hanging behind him into the cart, covered with stuff. Most obviously is when he turns at one point to wave or talk to someone (I forget exactly what) and his legs don't move at all with his body, as if they were glued down. Oh wait, that's probably because they were. ;)
- One of the more interesting visual tricks happens in the scene where Gandalf has come to visit Bilbo before his party, and Gandalf sits down and Bilbo pours him tea. Now, the reason this is so damn clever is because the actors aren't actually lined up and together. I'm guessing they just blue-screened* them together. Look at the little teacup on the table. Bilbo avoids touching the lid at one point, because it doesn't exist for Ian Holm. Gandalf lifts the lid, Bilbo gingerly pours the tea (not because he was actually that cautious, but because he's doing this against a blue-screen or something similar), and then Gandalf puts the lid down. Now, I only had a second or so to take this in, but I'm pretty sure when he puts the lid down it doesn't quite line up with the cup, or whatever that thing was. Why? Because again, he's acting against a blue-screen and probably just putting the lid down onto an entirely different cup, and when they matched up the two actors, they didn't quite line up right. It's tricky to get stuff like that perfectly lined up, and probably took a lot of takes just to get that close, but it was yet another trick I noticed.
- Finally, the obvious ones: a lot of scenes feature Gandalf, or a hobbit, but not both at the same time. Several of the scenes on the cart where Frodo and Gandalf are talking are like that, where they cut from the first's face to the second's face, and never get them both in the camera at once. Hey, sometimes the simplest tricks are the best.
[Addendum: It occurred to me I never mentioned the most obvious trick of them all: the fact that in every scene, items, furniture, houses, etc. were all scaled to fit the actors. When McKellan bangs his head on the candelabra, he's banging a smaller one in smaller hobbit hole than the one Holm just walked through a moment ago. Another obvious one, but worth mentioning.]
Now, there was other stuff too, but honestly I can't remember any more. I only saw it once and was trying not to puke at the time, so I missed a lot... but I noticed all of that just in the first part of the movie, and that was while I was distracted. Someone who knows more about special effects and "movie magic" who was paying attention would've seen those leap off the screen and slap them in the face, which is what bothered me about the special effects. The way I see it, special effects are best when they're like makeup should be - subtle, used to enhance what's there, not blindingly obvious and trying to cover up for glaring flaws. (See Mimi from the Drew Carey show if you need a refresher course in bad makeup jobs.)
The sfx in FotR felt sloppy, often, and didn't impress me. The CG work was often weak (although at times quite good; if they could've been more consistent it would've been nice) and the rest of it seemed to suffer from a lot of that. If you're going to use body doubles, make them look closer to the actual characters. If you're going to use CG rendered standins for some far-off shots, make sure your CG artists really understand how the human body moves, so they don't look awkward and ungainly.
Still, the movie was quite good, despite its flaws, and I definitely want to see it again. So don't get me wrong - if you can set aside the bad sfx at times, it's great, and I doubt if most people would be bothered by that sort of thing the way I was. I once wanted to be a CG artist, so I take special notice of CG pieces.
* - I know, they're often green nowadays, but the term still stands.