diff --git a/app/src/main/cpp/PhoneDevice.cpp b/app/src/main/cpp/PhoneDevice.cpp
index b231533b..9ce68663 100644
--- a/app/src/main/cpp/PhoneDevice.cpp
+++ b/app/src/main/cpp/PhoneDevice.cpp
@@ -1579,7 +1579,7 @@ bool CPhoneDevice::OnImageReady(cv::Mat& mat)
     }
     cv::Mat roi = mat(cv::Rect(lt2, rb));
     cv::Mat clrMat(roi.size(), CV_8UC3, scalarWhite);
-    double alpha = 0.2;
+    double alpha = 0.5;
     cv::addWeighted(clrMat, alpha, roi, 1.0 - alpha, 0.0, roi);
 
     // cv::rectangle(mat, lt2, rb,cv::Scalar(255, 255, 255), -1);