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Daniel Westlund wrote: Thanks and sorry for my late response. I still think it would be a good Idea to be able to set the color of the shadow catcher by hand and not always relate to the background image. //Daniel

just need to understand how this functionality should work and then we can probably do it

Evgeniy, the example from Cinema that you show presents a little bit different from what I understand as shadow catcher. In your example there are different material properties for reflection rays, camera rays and shadow casts. E.g. reflection rays from sphere see the checker that is not seen from camera directly).
I think it's a little bit different functionality from shadow catcher. Usually what you have shown is called RaySwitch material (e.g. in Corona) where you assign different materials for Camera, Reflection, Diffuse, Refraction, etc. rays. And there are also some features that implement exclusion of some 3D objects from reflections or camera or shadow casts from other objects. With all this flexibility and based on physical light transport under some constraints you may implement many interesting solutions. And it's possible to add these things to CentiLeo in the future.
What I understand as shadow catcher is a different thing a little bit. It is a tool to add 3D computer graphics objects inside a photo. And the essential thing is to draw shadows casted by CG objects onto the ground in the photo. You usually make a plane (or some more complex object) and place objects on top of it, enable shadow catcher and there you get shadows without additional illumination on the photo. Howefer, I think we can make the option to light source to add lighting on the photo (to the region with shadow catcher material). And it's also possible to make shadow catcher for alpha-channel only: on beauty it renders without background color on the plane but in alpha channel it still draws the shadows. What do you think about that?