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Shooting VFX Shots Against Black Duvetyne


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#1 Micah Van Hove

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Posted 17 December 2015 - 12:38 AM

Hey all, I'm DP'ing my first VFX centric gig and I've got a couple months to prep.

 

We are shooting in a large shared warehouse space. There isn't enough money to green screen everything, so we've planned on only green screening our set extension and shooting hanging black duve around the whole space. We will likely have one HMI (1800w), a 1K fresnel, and several 1x1 LED Panels. My questions are:

 

1) Do you have any lighting tips when shooting a set extension shot mixing green screen and black backdrops?

 

2) Any tips to keep light off the duve hanging everywhere (especially the floor)?

 

3) How to get the most out of the HMI lighting a large space (toplight with a butterfly?) 

 

I've attached some storyboards, any advice is appreciated!

 

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#2 David Mullen ASC

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Posted 17 December 2015 - 12:46 AM

Seems to me like you'd be better off just shooting everything against black and painting the floor black, then using smoke for the shafts of light.  At this angle, there is only floor or the piano anyway as the near background around the figures so I don't know why you'd need to pull a chroma key around them. The set extensions seems to be beyond the moving edges of the figures.  What does your compositor say?


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#3 aapo lettinen

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Posted 17 December 2015 - 07:15 AM

are the shafts of light going to be seen in the air in front of the cgi elements and what texture the floor (ground??) is supposed to have, if the ground is also cgi and not only black surface you need to replace all of it also under the actors. 

 

You can mask quite easily most objects which don't move so you would only need to green screen all if the shafts of light are seen and you can't hide the transition from shaft against black vs. black against green later in compositing. 

 

If you can add the shafts later you would only need to green screen the moving objects (the guitar player,  the piano player + moving parts of her dress) and you could mask+rotoscope the rest (the piano for example which is static) and do the shafts later.  If the camera is moving you would need to rotoscope all which can't be keyed and match the camera move to the other player's element, then match move in post to get the same move to the cgi plate. This again assuming that the ground needs to be cgi and not only pitch black surface without texture.

 

If the background really IS black without post texture and the cgi elements are outside the light shaft areas and moving edges it would be easiest to just shoot it all against black as David said  :)

 

I'd say it might be easier to add the shafts in post if the cgi is seen BEHIND surfaces which need keying/rotoscope and are IN the light shaft


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#4 aapo lettinen

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Posted 17 December 2015 - 07:34 AM

it is possible to shoot for example this way if you can add the light shafts in post. the piano may reflect green screen quite much if keyed fully so it might be simpler to key only the parts from it where the piano player's hair or hands go over the edges. the immobile piano edge can be rotoscoped (if edge lighted!) and thus just shot against black so you can get rid of disturbing reflections

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#5 aapo lettinen

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Posted 17 December 2015 - 07:42 AM

a small disclaimer: there is about a million ways to do these effects and camera move or lighting change from x to y may matter quite much so your cgi person will know best how to do these effects most efficiently :)

 

if your effect is supposed to be pitch black (without any texture) floor with edge lighted cliff area that could be done quite easily to the all against black footage (you still need tracking marks for the cliff and possibly match move=lots more markers if the camera move is big enough to change perspective considerably)

 

the pitch black areas also always have 'camera texture' (noise/grain) so it is a good idea to leave lots of headroom for masking if you can't fill all the frame with the same quality black


Edited by aapo lettinen, 17 December 2015 - 07:46 AM.

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#6 KH Martin

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Posted 17 December 2015 - 08:38 AM

Coming from antique-school (that's your grandfather's version of old-school), you could also do some in-camera enhancements to the light shafts, assuming you have static camera positions. That would involve ghost-glass (or just a high quality piece of glass) and reflecting in a drawn-on shape for the light shafts to embellish whatever practical light you use to hit the piano and guitarist. This can be as simple as cutting a tear-drop shaped piece of white or light blue posterboard and making sure it just misses on the depth of field or using the glass to reflect a chalkboard at right angles to the set on which you draw the light shaft. 

 

You could then power windows in post to amp up the light you did have that falls inside the light shafts.

 

I'm big on using garbage liner type material to create a metal-deck for flooring, so that is kind of a duvetyn approach to that part, only cheaper.


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