diff --git a/script/imgtest.py b/script/imgtest.py
index fe140ff..922d727 100644
--- a/script/imgtest.py
+++ b/script/imgtest.py
@@ -26,6 +26,11 @@ class MyFilter(Filter):
             
         op_image(output_puck, output_samples, "and")
         r,g,b = [0]*256,[0]*256,[0]*256
+        r,g,b = [],[],[]
+        for i in range(256):
+            r.append(0)
+            g.append(0)
+            b.append(i)        
         set_lut(output_puck, r, g, b)