Rigify: Unexpected deformation based on a given weight paint Okay, so I just ran into a weird problem I have no explanation for.I am used to the basics of skinning and weight painting bones to a certain portion of a mesh, but still I don't know what is going on in this case here:
I have a rig set up with blender's rigify add on (see the rig.blend file attached to this post). After creating the rig I parented my geometry with automatic weights which results in fairly good skinning most of the time. Anyhow, this time some deformation was weird, so I checked the weight painting and noticed some strange behaviour.
On the picture below you can see the skin weights applied for my DEF-forearm.R and my DEF-hand.R. From this picture alone I could expect a certain kind of deformation when rotating my hand for example ...

... but what I get is this ...

As you can see my upper-arm geometry is also deforming even though I only rotated my hand ctrl. The deformation bone for the upper arm didn't move at all but still the geometry associated with that upper arm bone is getting deformation from the hand bone.
I can watch this behaviour on all extremities within the rig.
Download the rig file here.
I think it's a usage issue, not weights of DEF-forearm.R and DEF-hand.R.
Because when I reduce the value of Rubber Tweak, it seems to work fine.