If we need to convert a ,sid to something editable, we convert everything to JPG's. It's a little bit of a pain because we don't use jp2 files but we open the .sid with MrSID Geoviewer. It's an older free program that isn't offered thru Lizard Tech anymore but you can Google it. The program will let you export the whole image or a portion of it and choose the resolution and also have it make a new world file for the whole or partial image. It'll convert it to a .tif Once we have it as a .tif, we'll save it again as a .jpg so the file size is greatly reduced. I then convert the .tif world file into a .jpg world file and I have a near perfect smaller version of the original .sid.