I have a recent Geoeye-1 image, sent as a 4-band (50-cm resolution pan-sharpened) TIF file - DN values, by the looks of them.  I would like to convert these to radiance & reflectance values for further interpretation.  What is the best process for doing this with ENVI 4.7 (if I can)?  Any help, hints, or warnings of pitfalls would be greatly appreciated. - Colin