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Green screen --> set the Kelvin (WB) , so the green matches the color-bar (vector-scope) green.


lenny87
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Hello there,

I am looking for a second opinion:

A local guy, who has his own professional green screen studio, advised me to adjust my Kelvin (WB) in the camera, so that the green from my green screen matches the color bar green. In other words it matches the green in the green spot on the vector scope. He said that it makes the keying much more reliable. After the keying the character has to be color corrected back to its original state.

The following pictures show:
-1x - the kelvin (WB) matched in the camera, so that the green hits the vector scope green
-1x - the Kelvin (WB) set in the camera with the use of a white balance card (so a proper WB setting)
 

Kelvin-to-match-color-bar-Green.thumb.gif.f5170e6b6a773222a32fe566025c3171.gif

 

Kelvin-WB-made-By-camera.thumb.gif.14f7f63283660df4f4f076431d9da19a.gif

 

My question is:
-is this a good idea or not? cause at the moment i can;t see the advantage of it, cause i tried keying both and i can't find an advantage keying the footage with the Kelvin (WB) set, so that the green hits the green spot in the vector scope.

I hope somebody can explain me why to do it? Or why not to do it?

Thanx in front
Greetz Lenny

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I had never heard such advice... and I sure would not follow it

Nowadays it is not strictly necesary to have a blue o green screen -some other colors could do- though it still helps, specially since those specific shades of green and blue are easier to key and not so close to the green and blue we find in every day life (clothes, skin tones, etc). Having said that, the color of your greenscreen material is way off...

The most important elements are different lighting and separation. You should have a set of lights to light the greenscreen and a different set of lights to light the subject. Light the greenscreen so that it presents an even surface on camera and light your subject however it fits the scene, context, VFX work, etc. Obviously, you should expose and WB to your subject! Then, if necessary, adjust the background (greenscreen) lighting. The longer the distance between you subject and the greenscreen, the better; separation avoids green spill in your subject. In exterior locations, it is easier to avoid and usually available room is no problem. In interiors, try to put as much distance as possible between subject and greenscreen, and cover with black cloth the parts of the greenscreen that are not in frame -they still reflect green light- and use a proper hairlight/backlight. I hope that helped!

 P.S. I hope that is not the guy's "professional green screen studio" because that is far from pro... the ceiling is too low and I can't see a truss or anywhere to hang the lights and the back wall should gently slope to the floor to avoid that 90º shadow line, not to mention the green colour is way off as I said before. 

 

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13 minutes ago, pablogrollan said:

I had never heard such advice... and I sure would not follow it

Nowadays it is not strictly necesary to have a blue o green screen -some other colors could do- though it still helps, specially since those specific shades of green and blue are easier to key and not so close to the green and blue we find in every day life (clothes, skin tones, etc). Having said that, the color of your greenscreen material is way off...

The most important elements are different lighting and separation. You should have a set of lights to light the greenscreen and a different set of lights to light the subject. Light the greenscreen so that it presents an even surface on camera and light your subject however it fits the scene, context, VFX work, etc. Obviously, you should expose and WB to your subject! Then, if necessary, adjust the background (greenscreen) lighting. The longer the distance between you subject and the greenscreen, the better; separation avoids green spill in your subject. In exterior locations, it is easier to avoid and usually available room is no problem. In interiors, try to put as much distance as possible between subject and greenscreen, and cover with black cloth the parts of the greenscreen that are not in frame -they still reflect green light- and use a proper hairlight/backlight. I hope that helped!

 P.S. I hope that is not the guy's "professional green screen studio" because that is far from pro... the ceiling is too low and I can't see a truss or anywhere to hang the lights and the back wall should gently slope to the floor to avoid that 90º shadow line, not to mention the green colour is way off as I said before. 

 

Thanx for replying,

The green screen room is my own DIY room. I know it is not perfect, but i am not allowed to get the ceiling out, and therefore i have to do it with this. The local professional has a huge Studio with a professional plastered green screen painted with color bar green.

My green screen is one, bought at a professional shop (its trevira cs material) used by lots of film studios. The screen and the character are both lit separately and i also have a backlight. I have ordered an X-rite color checker Video card and i guess that will bring back more green in my green screen :-) after using it.

Anyway you would advice me to use a normal WB, set with a white balance card?

Greetz Lenny

 

 

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6 minutes ago, lenny87 said:

Thanx for replying,

The green screen room is my own DIY room. I know it is not perfect, but i am not allowed to get the ceiling out, and therefore i have to do it with this. The local professional has a huge Studio with a professional plastered green screen painted with color bar green.

My green screen is one, bought at a professional shop (its trevira cs material) used by lots of film studios. The screen and the character are both lit separately and i also have a backlight. I have ordered an X-rite color checker Video card and i guess that will bring back more green in my green screen :-) after using it.

Anyway you would advice me to use a normal WB, set with a white balance card?

Greetz Lenny

Yes, you should definitely expose and WB to your subject -with a white balance card is perfect-, not the green screen.

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