View Full Version : An interesting effect, HELP?

11-14-2005, 09:29 PM
Okay so I only have iMovie at th moment and have no way to upgrade at the moment. Well I want to compose a scene were lots of people are running up and down the hallways while 2 other people are walking the other way. The thing is that I want the group of people to move really fast, while the people in the middle are walking normally. I was thinking that I would film 2 exact scenes and then just place one scene over another, is that possible? Or do I need to do something else?

11-14-2005, 09:36 PM
On big film shoots they would do something that is very expensive called motion tracking (actually I forgot the exact name of it)... Zach Braff briefly talks about this in Garden State commentary for the plane scene. They shot the party scene where its basically the same effect by having Zach move extremely slow and blink as little as possible. The result of both is what you are talking about.

I would think the latter is about the only plausable way to film it on a tighter budget.

This is a toughie though because the walking could be akward when sped up.

The only other thing to try would be to replicate the same shot exafctly and have the two in normal speed walking in front of a blue screen, or vice versa.

11-14-2005, 10:01 PM
Well I was thinking that I could film 2 identical scenes, but one have them just wakling, and then the second one would have the group of people, then just place then over eachother. Could I do that?

11-14-2005, 10:08 PM
Consider the problem. Either you will reduce the opacity of one greatly in which case either the people in the bg or your walking two will be ghost like, or you will have to split screen it, having the people walking on one side with your slow walking two on the other. I dont have Imovie but I think if you just cropped them both on the sides of the frame or something you could do this. As far as two people walking in front of a crowd going super fast behind, that could only be done one of three ways, motion tracking, the trick I mentioned earlier, or blue/green screen. The whole reason for green screen is to put whatever you want behind your subject.

11-14-2005, 10:26 PM
Oh okay thank you!

11-14-2005, 10:47 PM
You wouldn't know a place were I could get an opacity plugin for iMovie, which is also free?

11-14-2005, 10:53 PM
Sorry I'm a PC guy. In vegas you do whats called setting a video envelope which just allows you to go along the track on the timeline and set points - at the top of the track for 100% opacity, bottom for 0.

11-14-2005, 11:00 PM
iMovie doesn't natively support more than one video source at a have to buy plugins to get around this...they're not very expensive as far as software goes. You could get avid dv free (I have the link around here somewhere...I should hot key that) that does support more than one track and can do what you're looking's much more scary looking than iMovie, but the techniques are the same.

11-22-2005, 04:21 PM
what about shooting both scenes, and cropping out the edges of the walking shot? Make sure you match the film colour as best as possible, and perhaps grain out the walking footage to match the sped up footage (sometimes speeding up footage adds a grainy look).

11-22-2005, 10:22 PM
I think in iMovie you can do a barndoor wipe between two clips and freeze the wipe with some sliders. You could shoot the longer one and run it fast, then the other and run it slow in the middle as the frozen wipe acts like a split screen. Make sure you don't move the camera between those takes. Use a tripod!

11-22-2005, 10:50 PM
I always use a tripod don't worry. But the shooting is done, so yeah I figured everything out. I was unable to do the shot but I cnaged the whole commercial around anyways. Thanks though.