)
         log_string(f'wrote {image_name}')
 
-        nb_missing = sum( [
-            x[2] for x in picoclvr.nb_missing_properties(
-                descr,
-                height = self.height, width = self.width
-            )
-        ] )
+        np = picoclvr.nb_properties(
+            descr,
+            height = self.height, width = self.width
+        )
+
+        nb_requested_properties, _, nb_missing_properties = zip(*np)
 
-        log_string(f'nb_missing {nb_missing / len(descr):.02f}')
+        log_string(f'nb_requested_properties {sum(nb_requested_properties) / len(descr):.02f} nb_missing_properties {sum(nb_missing_properties) / len(descr):.02f}')
 
 ######################################################################