In your new graph each high value correspond to near distance... is like high value are inverse to distance ....if you use reclass in arctoolboxs can define por each class the value require ... here get a print screen done by me https://ibb.co/0KCj079 check there area different options to reclassify a raster...
Try to use image of the same date, and check the mosaic options in ENVI....perhaps could use ERDAS or another softwares and compared the results... regards.