diff --git a/hgdriver/hgdev/image_process.cpp b/hgdriver/hgdev/image_process.cpp
index f0061bf..07991d7 100644
--- a/hgdriver/hgdev/image_process.cpp
+++ b/hgdriver/hgdev/image_process.cpp
@@ -1814,7 +1814,7 @@ namespace hg_imgproc
 		}
 
 
-#define GAMMA_EX  2.0f
+#define GAMMA_EX  1.7f
 #define BLACK_OFFSET 8
 
 		void fittingLUT(const std::vector<unsigned char>& points, unsigned char min_value, unsigned char max_value, unsigned char* data)