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Matchmoving two dolly zoom shots with greenscreen


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Hi guys,

 

I'm gonna shoot next month a music video and need some thoughts about what to take into consideration for a particular shot the director is requesting. I'm the cinematographer and doing the VFX.

 

The shot (see picture): The main character is in a hallway and sees the band in a big hall. His goal is to reach the band, but bad guys tries to stop him. As the bud guys appear in shot we do a dolly zoom so that the distance to the band increases.

 

I would want to do this in one shot, but we have a hard time finding the right location with both the hallway and the hall. So we are thinking of doing this shot with a green screen and composite the two images in post.

 

We don't have enough budget to rent a motorized dolly so I'm a bit concerned how we are gonna make the shots match perfectly (focal, distance, dolly speed...)

 

Please share any input on solutions onset or for the post-production!

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I'm not sure I fully understand your question, but if you are saying you want to sync up two dolly/zoom shots without motion control I would get a stop watch and take a lot of measurements. Note your zoom speed. Measure the lens height and distance, make specific in and out points on the zoom, dolly, and focus. Shoot a little wider than you planned in case you need to reframe a bit. Then, with a stop watch, practice doing your move the exact same within a second or so. You can probably nudge it in post a little one way or another.

 

What I wouldn't do is promise the director anything you try is going to work without testing.

 

Edit:

And do a lot of takes to up the odds that two will line up :)

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What about just recording a wide shot of the stage
and using that as a flat plate in the greenscreen patch/doorway.

 

As the things zoom in/out you adjust the plane by scaling it or moving it
as a 3d layer in your compositing app, so visually you have the feel it matches your
hallway material. Simultaneously adjust the blurriness of the stage plane.

If it looks too flat, construct the stage as couple of layers in 3d space.
Cut some static parts as foreground, roto the musicians, some BG elements,

and all that combined with the motion of the virtual camera in you comp-app,

the defocusing, and it might work just fine.

 

Some shallower DoF might help here to smudge/mask things in the artificial set extension.

Best

 

Igor

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