diff --git a/MagickCore/magick-type.h b/MagickCore/magick-type.h
index e1b530f4c7..22e76b0898 100644
--- a/MagickCore/magick-type.h
+++ b/MagickCore/magick-type.h
@@ -116,7 +116,7 @@ typedef MagickDoubleType Quantum;
 #define MagickMinimumValue   2.22507385850720140E-308
 #define MagickStringify(macro_or_string)  MagickStringifyArg(macro_or_string)
 #define MagickStringifyArg(contents)  #contents
-#define MaxPSNRDistortion  (48.130803608679*((double) sizeof(Quantum)))
+#define MaxPSNRDistortion  (10.0*log10((double) QuantumRange))
 #define QuantumScale  ((double) 1.0/(double) QuantumRange)
 
 /*