Jump to content




Photo

Greenscreen and Overcast Day Effect

chinaball butterfly frame greenscreen

  • Please log in to reply
3 replies to this topic

#1 Sergey Block

Sergey Block

    New

  • Basic Members
  • Pip
  • 8 posts
  • Cinematographer
  • Europe

Posted 26 April 2015 - 05:36 AM

Hi!

I have 3 set-ups in a greenscreen stage:
- 3 girls walk on water (on 3m x 6m pool);
- walk on a wall of skyscraper (on 4m x 10m piece of mirror wall);
- stand on the roof of skyscraper.
All of this must be wide-shots shooting in different angles and movement of a crane.
This shots will be combine with shots of real river, real skyscraper and high angle view of the city.

I need some advice with greenscreen and day effects simulation.
In a stage I have to simulate overcast and sunny day. 
What is the best natural and simple way to simulate an overcast day: spacelights or big batterfly frames (or maybe something else)?

1) in the case of spacelights:
  a] is there any formula to calculate how many fixtures I have to hang by set area?
  b] any formula to calculate an exposure with spacelights?
  c] I want to add a little cool quality to a sunny day. Is it real to cover all (or half)     spacelights in 1/2 CTB? Is it common way?

2) in the case of butterfly frames:
  a] how much area of frames will I have to have (taking into account the set area)?
  b] will it be more naturalistic either light through frames (silk, etc...) or light in reflection?

3) I have several reflection surfaces in a set: mirror floor (4m x 10m) and waterpool (3m x 6m) and I have to shoot this set-ups in many angles. Are there any advices about working with such kind of surfaces and greenscreen/lighting approach etc.

4) can I use some lens diffusion with greenscreen?

Thanks for answers!


Edited by Sergey Block, 26 April 2015 - 05:38 AM.

  • 0




#2 Guy Holt

Guy Holt
  • Basic Members
  • PipPipPipPip
  • 511 posts
  • Gaffer
  • Boston

Posted 26 April 2015 - 06:28 AM

3) I have several reflection surfaces in a set: mirror floor (4m x 10m) and waterpool (3m x 6m) and I have to shoot this set-ups in many angles. Are there any advices about working with such kind of surfaces and greenscreen/lighting approach etc.

 

 

This is going to be difficult to accomplish in a studio. You would need a very large one in order to get enough separation between the reflective surfaces and the chroma key wall so that the wall doesn't reflect in the mirror surfaces. But then, you would see the studio ceiling and possibly even the lights reflected in the mirror surfaces. A better approach would be to do a simplified version of the Pinewoods Malaysia water tank pictured below.

 

pims_greenscreenwatertank_05.14_angle3.j

 

That is shoot outside on an overcast day with a 20x40 greenscreen rigged at a distance so it won't reflect in your mirror surfaces. This way you will see the actual sky reflected in the mirror surfaces. You will have very naturalistic even light for the overcast segment because you are using natural light.  The greenscreen will be lit very evenly by the natural light as well.  For the sunny day sequence, all you will need to do is add a large HMI to create some contrast on your talent.  As long as you don't use the HMI to back light your talent, it won't reflect in the mirror surfaces. To avoid the expense of renting a large diesel generator to power the HMI, you could use the new Arri M90, which has the output of a 12kw par, but will run on the 120A output of a couple of paralleled Honda EU6500 generators.  Since the M90 draws only 84A, you will have 36A left over for set power, which is more than enough.

 

Guy Holt, Gaffer

ScreenLight & Grip

Lighting Rental & Sales in Boston


  • 0

#3 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 18789 posts
  • Cinematographer
  • Los Angeles

Posted 26 April 2015 - 11:18 AM

I would go with a large array of Kino Image-80's, Blanket Lights, or LumaPanel fluorescents with daylight tubes, it's easier to get a cool effect that way without gelling space lights.  If you have the budget, you can blend those units even further with a large diffusion under them.

 

The reflection problems will be horrendous, and even if you shot outside, the problem is that the water or glass should be reflecting your background plates, not necessarily the real sky, though if you can use the real sky reflections, then shooting outside makes more sense if you can wait for overcast weather (once you throw a giant silk over everything, you have the same issues of seeing it reflected in some angles.)

 

An efx person may even want you to use a mylar floor to reflect the green screen under their feet but that won't work for high angles where you would see the lighting overhead in the floor.  In that case, the efx person probably wants a matte green floor as well, not a mylar floor.  But then if you have a matte green floor and no water or mirror surface, then the efx person is creating the effect of the water.

 

Otherwise, you can use real water or a mirror floor, just be aware that any high angles looking down at them will involve roto work to pull a key and get rid of bad/unwanted reflections of the ceiling lights.


  • 0

#4 Sergey Block

Sergey Block

    New

  • Basic Members
  • Pip
  • 8 posts
  • Cinematographer
  • Europe

Posted 28 April 2015 - 09:22 AM

Thanks for your answers!

It's a good ideat to build a pool outside! But, as I understand, it'll be not so good if I shoot a greenscreen reflection on the water or other mirror surface? (like on the picture below):

 

2015-04-27 13.51.36.jpg

 

That is why I should shoot a some kind of top angle in that pool?

 

 

In case of stage set what kind of lighting will you recommend to use for ambiance for high-speed shooting (300fps)?

And is there any approach to calculate how many fixtures I shoul hang per set area (20m x 40 m for example)?


  • 0



Also tagged with one or more of these keywords: chinaball, butterfly frame, greenscreen

Ritter Battery

Broadcast Solutions Inc

rebotnix Technologies

Tai Audio

Visual Products

Pro 8mm

Willys Widgets

CineTape

Zylight

Glidecam

CineLab

Rig Wheels Passport

Aerial Filmworks

Technodolly

Abel Cine

Paralinx LLC

The Slider

Rig Wheels Passport

Broadcast Solutions Inc

The Slider

Paralinx LLC

Glidecam

Abel Cine

Technodolly

Aerial Filmworks

CineTape

CineLab

Visual Products

Pro 8mm

rebotnix Technologies

Willys Widgets

Zylight

Ritter Battery

Tai Audio