That /MT setup must date back from when I tried to get all the speed I could from DistanceTransform, a year or so ago, which implied TBB compilation (and conflicts ensued with /MD) - without great success. At least this issue is solved - I have now to better understand the implications of this configuration parameter, should it be only for the pretty likely eventuality of my upgrading to 2.4.9 or 3.0 to check over speed improvements (multithread ?) available in DistanceTransform.