How to get Corona to STOP doing passes on the background image wasting resources

[Bracer]

When the render have a background image, corona renderer does passes on the background image wasting resources and time, I went to the bitmap setting in the material editor dialog and set filtering to none but Corona is still doing passes on the background image.

I would like corona to stop working on the background image and focus on doing passes on the 3D models instead.
How do I do that ?

Thanks.

[Tanakov]

What kind of image and how did you add it?

[Ondra]

it should already be happening, with the adaptivity. Some additional rays will be shot, but at about 1/10 of original rate, and processing them is ultra-fast compared to the rest of the image

[maru]

You can add CInfo_SamplingFocus render element to see where most and least sampling goes.