High CPU usage by a process called PTPCamera
So we found the Solution: 


Connect your iPhone/Camera and reopen Photos.app or iPhoto
Close iPhoto or Photos.app
Disconnect your iPhone/Camera
Open Photos/iPhoto again


now the PTPCamera Process should be terminated gracefully and won't spawn again in a busy waiting loop. 

You do not have to do this steps all the time, only necessary to terminate the process graceful and kick it out of the busy waiting state. How to come in this state, we (AppleDev and I) do not know.