Thread: Where can I buy a Gray Ball?

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  1. #1 Where can I buy a Gray Ball? 
    For VFX lighting reference.

    Thanks.
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  2. #2  
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    The Billups chart includes a black and white ball.
    http://www.dsclabs.com/vfx_visual_effects.htm
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  3. #3  
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    I did several CG shots on a horror feature of mine and could not find those reference balls either, so I ended up using large Christmas ornaments on fishing poles, I had a Grey scale colored one, and a mirrored ball. Worked great and the shots ended up coming out better than I had imagined.
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  4. #4  
    Senior Member Shawn Nelson's Avatar
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    Quote Originally Posted by Tony Warren View Post
    I did several CG shots on a horror feature of mine and could not find those reference balls either, so I ended up using large Christmas ornaments on fishing poles, I had a Grey scale colored one, and a mirrored ball. Worked great and the shots ended up coming out better than I had imagined.

    Do you have a write up of this? My brother is trying to do some fx shots and I haven't seen an explanation of using them.
    "Only those who attempt the absurd will achieve the impossible." -MC Escher
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  5. #5  
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    Unfortunately I don't, I just looked at the pro versions and noticed how much they looked like Christmas ornaments, or at least the coloring did, and knew they only need them for reference of where the light in the room is coming from and how that light effects the ball as you move it in the same directions as you want your Cg to move, so i bought them and sent pictures over to my CG company and got the ok. And it only cost me $5, plus the price of the pole, but you could use anything strong enough to keep the ball into frame. and another thing to remember is those balls come in all sizes some are bigger than your head.
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  6. #6  
    Quote Originally Posted by Adrian T. View Post
    The Billups chart includes a black and white ball.
    http://www.dsclabs.com/vfx_visual_effects.htm
    Thanks!
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  7. #7  
    Senior Member I Bloom's Avatar
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    Quote Originally Posted by Shawn Nelson View Post
    Do you have a write up of this? My brother is trying to do some fx shots and I haven't seen an explanation of using them.
    Shawn,

    It's best to get a ball that is half 18% gray and half reflective.
    You photograph the gray and reflective sides in each setup that you will be compositing in cg objects.

    Then in Maya, for example, you light a gray sphere and a reflective sphere to look exactly like the balls you photographed and then transfer the same lighting to your less simple CG objects and characters. The ball is also a guide to properly color correcting the CG objects when compositing them into the scene.

    There is also software that can extract light positions from your reflective ball. Not so necessary but it exists.

    Hope that helps,
    Ian
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  8. #8  
    Quote Originally Posted by Shawn Nelson View Post
    Do you have a write up of this? My brother is trying to do some fx shots and I haven't seen an explanation of using them.
    The gray ball explanation: If you know the gray ball is say, 50% gray, you can then in post create a CG sphere that is 50% gray and compare your lighting on the CG sphere to the real gray ball. Direction of light, color...try to get your cg ball to match the real one and you know your lighting is spot on.

    The chrome or mirrored ball has a dual purpose. It can be simply "unwrapped" to provide a simple reflection map. But the real gem is to get (or create via the RAW metadata) different exposures of it and create an hdr image file, and use that as either a reflection map or actual lighting data, or both.
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  9. #9  
    Digital FX Greg M's Avatar
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    We use large stainless ball bearings...much better finish. For larger shots the large garden gazing balls work ok...just be sure to get the stainless variety, nothing worse than cutting the hands of your vfx guy when the glass breaks.

    Here is a sample composite of a shot we are working on, this is a very early test shot...the final plates will be shot next week, and the 3d crawfish has a ways to go. Please save as:
    http://www.digitalfx.tv/images/crawfishtest.mov

    EDIT: Here is a shot of the ball I found still on the camera.

    www.digitalfx.tv


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  10. #10  
    Also another tip. If you're going to unwrap your ball into a spherical environment map I highly recommend Adobe Photoshop CS4. Its HDR tools are much better than HDR shop's. Saves a ton of time.

    Overall though I recommend using a fish eye and Autodesk Stitcher. That produces phenomenal results that blow away any ball.
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