diff --git a/plugins/GSdx/GSDeviceDX.cpp b/plugins/GSdx/GSDeviceDX.cpp
index f029cf28ff..f479288b14 100644
--- a/plugins/GSdx/GSDeviceDX.cpp
+++ b/plugins/GSdx/GSDeviceDX.cpp
@@ -154,6 +154,10 @@ bool GSDeviceDX::SetFeatureLevel(D3D_FEATURE_LEVEL level, bool compat_mode)
 // 1211 Cd*(1 + Ad) => Source * Dest color + Dest * Dest alpha
 // 1221 Cd*(1 + F) => Source * Dest color + Dest * Factor
 
+// Special blending method table:
+// # (tricky) => 1 * Cd + Cd * F => Use (Cd, F) as factor of color (1, Cd)
+// * (bogus) => C * (1 + F ) + ... => factor is always bigger than 1 (except above case)
+
 const GSDeviceDX::D3D9Blend GSDeviceDX::m_blendMapD3D9[3*3*3*3] =
 {
 	{0, D3DBLENDOP_ADD         , D3DBLEND_ONE               , D3DBLEND_ZERO}           , // 0000: (Cs - Cs)*As + Cs ==> Cs