My query is how to keep the poster resized while allowing my figure to move around the frame.
you need to duplicate the video and cut the guy from it. it's called rotoscoping = tracing over a moving image. there are several techniques to achieve that and you should do it in Ae, not Pr.
the main two approaches in Ae for doing that:
1. creating masks with key-frames on the main path movements and carefully correct, if needed, the interpolating between them - Managing and animating shape paths and masks in After Effects
2. Rotobrush - a tool for creating a matte through brush strokes and carefully setting up of different parameters - After Effects Roto Brush, Refine Edge, and Refine Matte
Hey, thanks for your response. I'm not sure I completely understand it. Are you able to further elaborate? Should I both resize the poster in Ae and also have my figure be able to move around on it too.
My idea (which I am not sure if it makes sense or works) was that I negate the rolling image from itself, that way the actor is allowed to move in front of the resized poster.
You need to cut out the guy one way or another and layer things together back again. There's no magic here. This is a fundamental, basic principle of layer-based compositing. I would strongly suggest you watch some tutorials on masking, rotoscoping and how to use mattes. You may also be able to generate a difference matte by layering the shot without the actor and the neutral one. Regardless, you need to read the help and look up the "big words". Your lack of knowledge is painfully obvious and you won't get anything done if you don't even know these basics.
Do you know photoshop? It's the same thing only Ae has a time factor. One layer is the cutout guy, underneath the enlarged poster cutout, underneath the original footage. now, since the guy is changing his movement (not like the poster which is static) you need to cutout through time - this is called rotoscoping. All the information is in the links I provided in the last response.
Well yes, that's why I'm on the forums mate. It's exactly why I'm here, to work it out. There's no need to be antagonistic lol. In the time you wrote that message you could have given basic principle steps, but you chose not to. Thanks anyway.
Thank you Roei for your elaboration. I know Photoshop quite well. I'll work it out from your links provided.
You're welcome. if you are comfortable with Photoshop, you will get the idea pretty fast. you can even Roto in photoshop for video! but not recommended in this case. if you are interested in a full based course, I would recommend the compositing series by Mark Christinansen on Lynda. After Effects Compositing 05: Rotoscoping & Edges though you should pace yourself. this is advanced stuff.
Thanks for the links! I tried a matte difference layer but there were a bit of problems, I may have to retoscope since its only a few frames
I tried a matte difference layer
the only way this would work is if you have the same footage underneath your character. then the difference matte cut out the difference. so this is not a good solution for you here. just rotoscope a few frames it's not that bad and look at the advice from the rotoscope section in the link I sent you. a common mistake is to work frame by frame - don't do that unless the movement is very fast and abrupt which I believe it is not. and use a touch of feather.