Motion Blur limit to one object in scene? and blur in PS over multiple frames?

[rich0550]

Sorry I am stumped. I tried enabling disabling in object properties. But does not exclude certain objects from motion blur. How can I have only one object or selected objects blur with motion? Thanks. Also what is best practice for getting a blurred blade into photoshop. Is velocity channel the way? If so it only blurs the object in its one frame would need the blur following the blade path.

Thanks!