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View Full Version : VFX field gear -advice needed


pekko
03-21-2005, 02:43 PM
Hi

I am on the big movie project that requires lot of cg. And i was thinking to build some sort of set of probes for the shooting so that i can have as much as possible the information out from the location shootings. i would like to ask few questions about how these things are done usually:

-Chrome ball. Do one need that for something else than just HDR -based lighting.

-Grey ball. Is this better than chrome ball for aquiring scene lighting? do i need both?

-Color plates. I have seen those on many making ofs. People show colored cartoon pieces for camera. When one know cmyk values one partucluar piece, what kind of things can be judged from that?

black and white grid. I was thinkin to get grid on the cardboard and shooting few frames of that board with the camera and lense that is used, in order to get the lense distortion irformation. Any comments?

vrljc
03-21-2005, 08:29 PM
One other use for a chrome ball is for light and object placement. That way when you get back to the studio, you dont go, "Crap! Where was that light placed in relation to object X?"

Also, I use a chrome ball or another reflective surface like metal or ceramic for capturing your spec hi-light intensities/values. This is only necessary if you have a 3D object that actually has a bright spec hi-light.

I use a gray ball for aquiring shadow values and for light color/intensity values. You can actually take the image of the gray ball into photoshop, then sample the values on the ball and use those color values as a base for your lights' colors. Especially for the shadow values, the gray ball is probably better to use than the chrome ball.

Good idea about the black and white grid. I should try that sometime.

-jon

pekko
03-29-2005, 02:26 PM
thanks. I try to get both: the chrome and the grey ball.

I am still thinking that would it be any good to show camera some kodak test cardboards? like the one with middle grey and tone ramp. Would they be any usefull for compositing CG to the live action plate?

Varinder
04-28-2005, 05:41 AM
Where can you buy the chrome and grey ball? What type of material is the grey ball? I'm also looking for these objects in order to shoot a lot of cg stuff myself.

Also, can someone explain the full proper use of using the chrome ball and grey ball? How you use it, when you use it, why you use it? etc. I only know so much about it right now and i'd like to learn more about it.

Hugh
04-28-2005, 09:59 AM
The grey ball is to give an indication of the diffuse light that is falling on the scene. Usually only used for reference - render a grey ball in your scene and compare the lighting on that with the lighting on the grey ball that was actually shot.

I asked people for advice on what a VFX Supervisor should carry around with them on my blog (http://www.brokenpipefilms.com/unframedvfx) a while back - here is the specific post (http://www.brokenpipefilms.com/unframedvfx/2005/03/vfx-supervisor-carry-kit/) with some useful comments at the bottom.

Also, some good links for places to get chrome balls from (http://www.brokenpipefilms.com/unframedvfx/2005/04/chrome-ball-where-from/) (although I can only find these in the US - if anyone knows where I can get one from in the UK, it'd be much appreciated...)

vrljc
04-28-2005, 02:18 PM
I made my own gray ball. I bought an 8 inch styrophone ball, added about 10 layers of gesso to it and constantly sanded it to smooth it out. Then I went to Home Depo to buy some 50% flat gray paint and painted it. Dont spray paint it, you cant get smooth color.

As for the Chrome ball, go to:

http://www.dube.com/ball/8.html

Note that these are ball bearings so they are solid steel. This is a lot better to use than a gazing globe because not only are gazing globes not perfectly smooth like a ball bearing, but one drop off the tripod and it will shatter, dent, scratch, etc.

One unfortunate thing about the ball bearing though is that they are smaller and cost a bit more. However, they are better quality for an HDR (because they are smoother) and if you have a 300+ mm lens, then the size of the ball doesn't matter.

-jon

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