Depth map is no good with motion blur, how to improve?

Hi,

I want to render an animation, and wanted to use the depthmap for post production effects. I also want to use motion blur on the "diffuse" frames.

The depthmaps when rendered with motion blur is useless and wrong.

1. Is it fixable with a setting in poinTools?

2. Assuming no, can I render just the depthmaps?

Here is how the depthmap looks when motion blur is added to the diffuse frames:

(please note they are both saved in JPG because this forum does not allow BMP to be uploaded)

Here is how it looks when NO motion blur used:

(better but still horribly banded, good enough for my purpose but still really bad)

What to do???