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Forced Perspective

forced perspective music video vfx green screen a7sii cinematography hiro murai

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#1 Sam Oddo

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Posted 04 June 2016 - 09:51 AM

Hey Guys,

I don't really have a vfx background, and it would be fantastic if you could help me out! Attached below is a still (and a link to a video) of what I am trying to achieve. I'm looking to shoot a music video that uses forced perspective (mainly band performance stuff), and I am not quite sure how to go about making it look right. To give a little more context, I'll be shooting with an A7sII camera. My questions are as follows:

1) Did they use a green screen for the people?

2) How do you make the person match with their background? I know lighting is a huge part of it, but I'm referring more to field of video, camera angles etc. Is there an equation that involves the height       of the person/building, camera focal length etc.

3) Some of the shots in the video are moving... Is this a fake camera move done in post? Was there a lot of compositing involved? Can this be done practically without heavy post work?
 

4) I've read that if you're trying to make a person look large, you should film them in slow motion to give the illusion of a large body moving. My question here is with my camera's sensor constraints: I       would like to shoot the back plate in 4k for maximum sharpness and better grading (shot full frame),     but if I film the individual in slow motion, I'd be working with the equivalent of a super 35 sensor.           How can I reconcile the two images to make sure that they visually match?
 

5) Say I shoot a scene that is back lit: I would have to incorporate the shadow of the person in the shot. Any tips?
 

6) I need to do this on a small budget: Any tips on achieving a good product cheaply would be greatly appreciated!

I know I asked a lot of questions, but I'm having a difficult time finding the information I need online. Thanks for your help!

-Sam

 

Link to video: 

Attached Images

  • Screen Shot 2016-06-04 at 10.49.10 AM.png

Edited by Sam Oddo, 04 June 2016 - 09:54 AM.

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#2 David Mullen ASC

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Posted 04 June 2016 - 10:08 AM

I wouldn't call this forced perspective in this case -- I mean, it would be if the foreground city was a miniature meant to look full-size, but in these cases, I think the foreground IS full size and the person is composited in post to look huge.

 

There are in-camera ways of making someone near the camera look farther than the background but if you shoot the person head-to-toe, then you have the problem of what they are standing on being in the shot, so this sort of trick works better, for example, of the person is standing on a platform on a miniature ground with maybe miniature trees behind them on one side of the frame, and that platform blends into a real size landscape on the other side of frame.

 

So in this case, it would be easier to do it in post as a composite, but then you get into the issue of how good can you do chroma key composites.

 

Ideally, the focal length of the lens used would be the same for both the foreground and the person, you'd just have to calculate the distance and lens height to scale that person.  Imagine, for example, that you were making the person look 10X taller, so if the camera were 10' in the air for the shot of the buildings, it would be 1' off the ground for the person.


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#3 Sam Oddo

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Posted 04 June 2016 - 10:14 AM

Thanks David!

I have a reasonable proficiency in After Effects, and feel that I could adequately composite several elements together: I just wasn't sure of how to actually film it. I see your point with the "head-to-toe" compositing issue; however (referencing the attached still), could I just use backplates that obscure the individuals feet to get around that? Would you also know how to film a person on green screen in such a way as they blend (in terms of height/angle etc.) with background elements like a building or mountain?

 

-Sam


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#4 David Mullen ASC

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Posted 04 June 2016 - 10:16 AM

See my last paragraph that I added before you replied.


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#5 Sam Oddo

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Posted 04 June 2016 - 10:25 AM

That helps a lot, thanks!


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Also tagged with one or more of these keywords: forced perspective, music video, vfx, green screen, a7sii, cinematography, hiro murai

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