I never came back to report on this, but yes, the ringing was substantially reduced with this change. The change merely disables edge enhancement completely. So it seems that by default edge enhancement was on, with no means of changing it.
We also had to disable the lens shading in the ISP file. We use different lenses than the ones provided by Leopard, so the profile was inappropriate.
We’re still seeing a bit of ringing, however, but I haven’t found any other settings I could disable to remove it.
RAW16 output does not show this ringing, and the image is softer, so I feel there might still be some sharpness enhancement going on in there somewhere. At this point, we have moved on, using raw16 for some tasks that are sensitive to the ringing, but that has other problems.
It would really be nice if NVIDIA opened up their tuning tools to knowledgeable power users that aren’t necessarily camera OEMs… our company sits between OEMs and the end consumer and it would make sense for us to be able to tune these characteristics to our needs.