Feb 19 2015
This is a cool little gizmo if you are trying to neutral grade your shots and the cameraman has taken a shot of a color reference card at the head or tail of a shot.
Here is a video on how it is used.
Here is a link to Marco Meyers website where you can get more info and the gizmo itself (click image below)
The RenderBlog also has a good tutorial on using the gizmo to get results better than photoshops camera raw (click image below)