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How to remove people/ cars in video

removing people in video masking visual effects final cut 7 after effects

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#1 Fran Tilley

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Posted 26 November 2013 - 06:55 AM

Hi All,

 

Would really appreciate help with this question:

 

How can I remove people and cars from a video?

 

I am going to be filming historic architecture in a very busy populous area (a city square) in Africa and would like to only show the buildings.

 

Is there a particular way I should prepare to shoot this? e.g on a tripod so it is a still capture?

What are the steps to take when i'm editing?

 

I am working with a canon 7d, fcp 7, have after effects but really not familiar with the workflow of importing files onto after effects or using the programme. Any step by step explanation in layman's terms would be preferable!

 

 

Many Thanks!!


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#2 aapo lettinen

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Posted 26 November 2013 - 07:49 AM

practically you are compositing a photoshopped still frame (buildings, streets) and various moving elements together (clouds, palm trees, etc.)

 

Maybe you can take some time lapse on a tripod and then composite the buildings from various frames (then you can restore the elements which are behind people when they are moving) , and shoot also some live motion and composite the desired moving elements to the final image.

 

You could also shoot time lapse with very long shutter speed, so the motion blur would hide the moving parts of the image (people, cars, etc.) , and then composite the clouds and palm trees to the final image :lol:


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#3 Phil Rhodes

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Posted 26 November 2013 - 10:05 AM

Hi Fran

 

If you shoot it as a lockoff (that is, no camera movement) it should be possible, although perhaps a bit labour intensive, to lose elements from the scene, so long as you have sufficient clean, unobscured background images of the subject you actually want to see. This is a relatively straightforward trick to do, although you do need to shoot it absolutely static (or, if you're very rich, using a robotic motion control camera, to achieve several passes with the same precise camera motion, but that's way beyond what it sounds like you're talking about). It was done for a short film called 405 where they needed an empty stretch of roadway, and you can see how here: http://405themovie.com/makingof04.asp

 

You should shoot very much more material than you think you need, especially if there are additional complexities. Things like smoke or dust drifting in front of the scene will obviously make life difficult, as will anything that moves on the subject you do actually want to see. Reflected light and moving shadows can also be a problem. If you've never done it before, I'd suggest shooting a test of any convenient building, and getting to work on it in After Effects with masks and a bit of rotoscoping. I can't really take you through it step by step, but you seem to have the basic idea.

 

P


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#4 Carl Looper

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Posted 30 November 2013 - 11:06 PM

Yes, shooting with a locked off camera is the simplest way.

 

You can then run an algorithm over all the frames to remove anything that is moving from each frame (leaving empty space). You can then populate all of the empty spaces with information from other frames where the same space is not empty.

 

Of course, anything standing still in the frame, that you don't want in the result, will still turn up in the result. These you would have to manually remove and populate with information from other sources - or just invent some plausible information to infill it.

 

Another way (far more elaborate) it is to take a lot of photographs (and I mean a lot) from different angles and run a 3D reconstruction algorithm over it. These algorithms remove inconsistencies (such as people walking through shot) leaving behind a 3D model of what was otherwise static (was otherwise a rigid body) in the scene. Can takes a long time to generate a high quality 3D model from the photographs, but the benefit is that you can then design and render a tracking shot. Work in this area is still an ongoing thing - but archeologists and those working in forensics are nevertheless using it and new techniques are always evolving. It's called "photogrammetry". So while the results may not be currently that great (although certainly not bad) shooting in anticipation of future algorithms becoming available won't hurt.

 

And one can always give the photographs to a good 3D modeller to work with, to recreate the scene.

 

C


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