Cycles render time increases drastically upon adding simple planar backdrop I have made a simple studio setup to showcase a toy car model. In Cycles I am getting an estimated render time of about 1 hour which is unusual for a scene this simple. Upon making tweaks I realised that hiding the studio backdrop from the render cuts my render time to 8 minutes.The backdrop is a simple beveled plane consisting of 36 quads. I have my max bouces relatively low as well as the indirect light clamping

This is the shot I am trying to render in Cycles as rendered in EEVEE

This is the size of my backdrop

And here are my render settings, which seem pretty tame all things considered.

Nodes for the cove.
The render-time difference isn't too surprising, given that without the background most of the camera rays would simply miss all of the geometry and so those tiles to the side would render extremely quickly compared to the rest. Adding the background means that those camera rays hit a surface and Cycles then needs to determine Diffuse rays from the rest of the geometry to shade each point on the surface.
One potential solution would be to use the new(ish) Adaptive Sampling option. This way you can set a noise threshold and those tiles far from the &quot;track&quot; should render quicker than they otherwise would, while still having enough samples to avoid noise.