Remove backplate from colour mapping and exposure control

Is there a way to exclude either the image plane, or the framebuffer background image from being affected by colour mapping controls and also excluded from framebuffer colour corrections? When Ive got a car shot with a cg road / foreground, but an image plane background, I want to adjust the car to fit to the image plane / background image. If the background image gets changed by my colour mapping tweaks, then I dont know if the car is actually matching or not.

Im using Vray 3.6 in Maya 2016. Cheers.

You can load it as a background image through the frame buffer itself, in the Corrections control panel.
I think there are plans to enable actual compositing in the frame buffer, this is the way to do it as it is.

Thats currently what Im doing. I dont use Maya image planes for anything apart from camera matching. But colour mapping / tonemapping in Vray still affects the background image in the framebuffer.

Hmmm, maybe I had a rogue image plane enabled. But today it seems to be working as I expected and the loaded in framebuffer background is working independently of any colour mapping. Mustve been a glitch at my end.