Help on Mirror ball, grey ball and macbeth chart

[blacknight]

HI guys

I saw the mirror ball, grey ball and macbeth chart used in a movie... can anyone help me out with the proper procedure to use these thngs( mirror ball, greyball, macbeth chart) in a shoot.

[Hugh]

A Macbeth chart will tell you the colour of the light, and any effect that the filters/film stock has on that colour. It will also tell you whether the film stock and processing are messing around with the overall colour (saturation, etc) so that you can match your "clean" CG to it.

The two balls are for getting the lighting that's coming from different angles to fall on your CG. The grey ball tells you what the diffuse light is, and the reflection ball tells you the specular/reflection. A well shot HDR reflection ball image can be turned into an environment light around your CG object.

A good test of CG lighting is to render a grey diffuse ball and a silver reflection ball in your scene, and compare them with the same ones shot on set, and see how they compare.

[blacknight]

Thanks Hugh ... which camera should i use to tak the 2 balls (arri or still camera) ?
wht if the camera(arri) moves in the stage with different center points, whr should i keep the balls n take the picture?

[Hugh]

If you can get multiple exposures with a stills camera to get a higher dynamic range, then that'd be ideal. On big shoots where they don't have time for that, though, I've often see them being shot on the main unit camera.

To be honest, it really depends on what it is you're wanting to put into the scene.

Are you in a position where you're about to go out on a shoot for something? If so, you want to talk to the person who's actually going to be doing the lighting on the CG whatever-it-is. They'll know what they want, and can tell you.

[Gentle Fury]

yeah field charts are a must when comping cg or 2 plates (tho they are so rare to get) it just makes it a LOT easier to match up pre-determined colors than abstract colors in an image.

[MrMovie]

Always best to get reference footage (balls, charts, whatever) from the picture camera. That way you take into consideration anything the picture camera is doing to influence the image (filters, film stock, etc.)

[blacknight]

im the one who wants to implement it on the future shoots i go for, b4 i go to my lighting guy i hav to knw the correct procedure right ... thanks gentle fury, MrMovie.

[Hugh]

Yes, it's good to, as MrMovie said, get whatever information you can. But your lighting guy will still be the one who uses the data, and will know the best kind of data that, in an ideal world, he'd receive from you.

When it comes to taking the images with a stills camera or the film camera, it depends what you're making in CG. If the CG object/character stays in roughly one place in the scene, then you'll only need the one set of images for the lighting. But if it moves around different parts of the set, where the light is different, then you'll either need lighting information for each section, or, as I have seen done, if the camera is following it, have the camera move done with you walking around with the reflection ball. Then the lighting can be recreated for any part of where the CG creature might be in the scene.

[blacknight]

thank u HUGH... ll talk to my lighting guy. cheers

[hugo_guerra]

And don't be afraid of looking silly walking around with reflective balls on set, even if you don't do that, they will still think you are the crazy fx guy that will mess up there filming schedual. LOL
Believe me, doing that will save your ass later on in the 3d stage and comp.

[MrMovie]

And don't be afraid of looking silly walking around with reflective balls on set...

If your balls are reflecting on set, you might want to put on some pants.

[blacknight]

lolz... ya thts true, thy treat reflective ball as a alien thing. hopefully some director's & dop's understand its real use & helps us out.

[dudekill]

Anybody know where I can buy a gray ball? I haven't been able to find one.

[MrMovie]

Anybody know where I can buy a gray ball? I haven't been able to find one.

Buy a chrome sphere (a.k.a. gazing ball) and paint half of it gray. That way you have both a gray and chrome sphere by simply pointing the appropriate side to the camera.

Here are some sources:

http://www.gazingglobesandballs.com/index.htm located in Alabama

http://www.yardiac.com/ in South Carolina

http://terradisiac.com/ in Ohio

http://www.sundialworld.com in Virginia

http://www.snappdragon.com in Tennessee

12" diameter is good for most situations, for close ups you can go smaller.

[dudekill]

Thanks Mr. Movie,
I do already have a gazing sphere. I was just wondering if anyone sold a gray ball specifically for doing vfx work, but I guess not. I will probably buy a wooden sphere and paint that instead. I think I saw some at a craft store. Thanks again for the great links.