Hi I have a 7.5 ds nitris and I would like to capture tapes shot on panasonic hd in slow motion. do i have to use an image conveter?

I would say yes.  The DS hardware either Equinox or Nitris will record what ever you send it.  You have to send it slow-mo for DS to capture slow-mo.

Where the Panasonic Varicam is set to "overcrank" the video for slow-motion sequences, I have used Final Cut Pro as an intermediary tool to recover the footage. I would capture using FCP and then output the result to a separate tape and ingest that footage into DS. For off-line, I'd ingest to MC and then on-line capture to timeline as one normally does on DS.