Sparse image grows beyond actual data?

[jamart]

I have been using SuperDuper to backup to sparse images created with Disk Utility to potentially expand to the full size of the original volume. For my needs, I like this approach better than Retrospect.

I recently noticed that the sparse image continually expands with each backup to far beyond the actual data written into it. Aparently the new/changed files is written and then the old files are deleted but the disk image does not release the empty space.

Is there a way to retrieve the disk space being retained without data by the sparseimage?

Thanks

John