Hi Jeff, thanks for the reply. I'm not using a signature from another file, just performing a normal Interactive Classification for each image. I don't have that much experience with ArcGIS, but I understood that the reject fraction was involved only when performing a Maximum Likelihood Classification. Is it also involved when running the Interactive Supervised Classification? If it is, I don't see why it would have happened just for this layer. Anyway, redoing the classification would take a very long time, is there no other way to rectify this problem?
Thanks,
Graham