This posting used to have the tag “– Except for Grayscale?” appended to the end of the title. That is no longer needed; see the bottom of the post for an explanation. We have been implementing University of Michigan’s DLXS software, and DLXS uses JPEG2000 for its image masters. We have been investigating reports of perceived changes in images in the conversion from our old media server to DLXS, and along the way I discovered an important fact: the default parameters for two popular JPEG2000 codecs results in an irreversible transformation. Here is how to address that.