Changing the color of a fast moving car

[Gohanto]

Hello, I've got a shot I'm working on that's proving rather difficult. I've got a telephoto shot of a character walking shot from just across a street with a 60i camera. A car drives in front of the camera, but the car is Gold and I want to change it to look like a green car (echos theme of greed throughout the movie). Because the reflections of the car's paint and the significant amount of motion blur, I'm having a lot of trouble in keying only the car's color.

Can anyone offer some advice?

 

[Shepi]

I would try roughly rotoscoping the car with quite high value of mask feather, and applying filter that changes selected color. Or just changing hue. If the feather is great, there shouldn´t be a visible problem.

 

[Matt Grunau]

depending on what is around the car, and what color's you want changed, a simple garbage matte may suffice to isolate it. Then pick the channel you wish to alter in the Hue and Saturation controls and have at it.

To avoid any potential artifacting due to color shifts, think about using 16 bit mode or switching to YUV color space. That may help. Or, use an adjustment layer with Hue and Saturation on it, and set its blending mode to color. I dunno why, but that often makes it look more realistic and give less artifacts.