I don't understand what happens here

Hi,
i’m pretty new to Blender and am trying out little projects.

I’m working on the follwing scene and don’t understand the lighting.
Here you can see the scene :

The shadow of the joint of the curved tube depends on the position of the camera and not only the emitter.
This picture is the intended camera angle and you see that the joint on the right tube throws shadow on the horizontal part, althoug the emitter is right above the horizontal tube.


By changing the camera angle, the tube gets lighted more as it would in reality :


Can someone eplain me what happens and why?

Thanks in advance
Thomas

Looks like a smoothing error. To test, make the object flat shaded and render again. To fix, make a cut in the pipe right next to the fixture bump that you created there so that Blender knows where to stop smoothing it.

Sorry for the late reply.

It is indeed a smoothing error.

Can you explain me how to do the cut?
Do I understand that right that I should have 3 objects instead of one and then only smooth both pipes? (pipe, fixture, pipe)

I got it.
I used the rip-tool (V-Key) and seperated the mesh in 3, but still in one object. I then flattened each mesh.
Was there a better way to solve this?