diff --git a/scripts/common.py b/scripts/common.py
index aa317c20dd021786866e057e440225694905bcec..f94c581a4ff5fdfb458000c8f9f7d781316bf8c9 100644
--- a/scripts/common.py
+++ b/scripts/common.py
@@ -184,7 +184,6 @@ def trim(error, skip=0.000001):
 	return error[skip:size-skip].mean()
 
 def luminance(a):
-	a = np.maximum(0, a)**0.4545454545
 	return 0.2126 * a[:,:,0] + 0.7152 * a[:,:,1] + 0.0722 * a[:,:,2]
 
 def SSIM(a, b):