separate subject from background without color screen?

[beaker]

Make a cleanplate of the background. Roto the guy out in your favorite compositor(AE I assume since you on the AE forum). Then place him back over the Cleanplate. Do the effect you want to the cleanplate and add noise/grain to it at the end so it looks like it was shot for real.

[shy-guy]

Thanks beaker,but rotoscoping its kinda what i explained,doesnt it? you mean take the guy out in every frame of the shot.... so there´s no other way?? whats the easiest way to do the roto in after effects? i´ve never done that, although i understand how it works, and how time consuming it is.

[Integrity]

In the way your wrote it sounds like you haven't recorded the shot yet, and since you said the camera would be fixed...when your out there doing it, record the street alone without the guy when there's no movement, then do your actual acting with the guy without moving the camera in between shots. Then bring these two in After Effects and put the footage with just the street below the one with the guy acting, and put a difference matte on the guy acting one. Select Matte Only in the View setting and the lone street layer as the Difference Layer within the effects settings. This is your mask for the guy acting layer, which will allow you to do whatever you want behind him without have to do a rotoscope.

EDIT: Sorry about that, had some things reversed. Fixed it now. Read it again.

[shy-guy]

Thanks Integrity; well not, i havent recorded the shot, but as i stated above, im having problems with the difference mate.. maybe its because im testing it with videos recorded from my digital camera?? i dont have a video camcorder, but a friend of mine its gonna loan me one the day of the shot; but for now, im making test with what i have; you know that videos taken from digital cameras look horrible (really noisy) comparing to a good camcorder, maybe thats why my tries at difference matte havent work?? I did the difference matte just the way you explained a few times and i haven´t had good results yet

[shy-guy]

Look, here´s what i´ve got with difference matte so far; instead of having the shot of me separated from the background, i become a really weird ghost.


http://tinypic.com/dzh4k7.jpg

[Integrity]

I'll try again, it's most likely I screwed up or something. I'll use your test this time though. I am using After Effects Pro 6.0 in case it deals with anything.

Import both videos, the one with you moving in your room and the one with just footage of your room alone, without you in it. In both of them the camera should not have moved. Move both of them into your composition and put the layer with you in it on top of the lone room. Then right click on the top layer (the one with you in it), and in the menu goto Effect > Keying > Difference Matte. The default settings should automatically work and at least some part of you should disappear. Make sure the View setting is at Final Output and change the Difference Layer setting in the Effect Controls window to the bottom layer, or the one with just the lone room. You should reappear. Now just for the heck of it import any file you wish to test out if you can put stuff behind you. A picture, another video...but put it in between the layer of you in your room, and the layer with just the room. Play with the Matching Tolerance and Softening and even the Blur to improve the matting.

Make sure the camera is set on manual control...basically just make sure the exposure does not change. In the example you gave I don't see much noise but that's probably because it's just a single frame. There are a bunch of techniques to get rid of noise but it depends on if the extra settings can deal with it. I tested this on some simple images moving that I rendered out in After Effects to see it it would work and it did, but that's because everything was sort of perfect, and also because I didn't take any real world images.

[shy-guy]

Well thanks integrity; i still dont get any good results with difference matte, but anyway, i´´ll just have to wait and see how this will come out with the video recorded from the camcorder that im gonna use; any others advices are welcome

[JoshKirk]

The cool thing about after effects is you can set keyframes. You dont have to do EVERY frame. Just do frame 1, then set a keyframe, then roto frame 5 with the same mask object and set a keyframe, AE finishes the other 3 for you.

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