First, I should make clear that I am not referring to Matrix-effects, bullet time, whatever you want to call it, which, surprisingly enough, I do have a decent grasp on, and which is explained fairly clearly and extensively across the internet.
What I mean are scenes where a character is walking through a scene with a lot of moving people, objects, and so on, and everything but the character freezes in time, as seen in Heroes, X-Men, etc.
The part that really baffles me is the interaction with objects carried by people who are frozen. For instance, there’s a commercial here where a guy is walking through a restaurant when everything stops, and he takes a pen out of one frozen person’s pocket. It’s clearly a stop-time effect, and not just people standing really still (I feel confident that I can tell the difference). There’s another where someone walks through an office, and everyone stops, including one guy who is in the middle of dropping a stack of papers. The papers freeze in mid-air, and the active person pushes them back into a neat pile in frozen dude’s hands.
I feel that the basic concept of how they do this should be fairly obvious to me, but I simply can’t get my mind around it.
I have wondered about those effects as well and look forward to someone coming by with a definitive answer. My guess would be that the moving person is composited onto the still scene and interaction with other objects would be computer animations.
The time-freeze thing can be done with the same apparatus. Snag the same moment from a wide range of angles and you can appear to pan around with time frozen. Add a live actor (filmed by a camera that pans in the same way as the fake pan) with a matte, or digitally. Interaction between the actor and the frozen scene can be done using a cut to a close-up of just the pocket and the pen, on a mannequin, or again, can be painted in digitally.
In fact, this effect did actually appear in the first Matrix movie - when Morpheus tells the construct to freeze in the crowded city scene.
I’m not sure if this is the effect you are asking about, but a few years ago there were some commercials where all action froze while the camera appeared to keep moving, showing the scene in 3D from a changing angle. One way this was done was with a lot of separate, still cameras placed in a line, all pointing to the same action center. They were fired simultaneously, then the still frames strung together to make a movie.
This only works for a few seconds (unless you have thousands of cameras), but it is a wonderful and impressive effect due to the 3D elements.
Nowdays there may be more sophisticated ways of doing a similar thing using CGI for all I know.
For those of you who actually want to see it step by step…This is a basic example, more complicated versions obviously take longer than 5 minutes or so!
In some instances, it really is done by people standing still. One sequence in Hereos has Hiro Nakamura freeze time and the camera follows him among the frozen people, including a girl jumping rope caught in mid leap. The behind-the-scenes footage shows that this was done by having the girl sit up on a green screen pillar, with the jump rope held up over her head by wires.