Make --filter and --exclude incompatible

photometry.py

@@ -505,6 +505,17 @@ def main(arguments = None):
     if not options.uncimgk:
         options.uncimgk = None
 
+    # There is not much point in using --filter and --exclude at the same time:
+    # the former discards all the images not taken in one or more filters, and
+    # the latter discards the images taken in one or more filters. We should
+    # always need to use one approach or the other, but never both at once.
+
+    if options.filters and options.excluded_filters:
+        msg = "%sError. The --filter and --exclude options are incompatible."
+        print msg % style.prefix
+        print style.error_exit_message
+        return 1
+
     # The annuli JSON file (that generated by the annuli command, and specified
     # with the --annuli option) must exist. The use of this file automatically
     # discards whathever was specified with the Aperture Photometry (FWHM and