diff --git a/a_scanner_darkly/main.cpp b/a_scanner_darkly/main.cpp
index 4bbd9ee..eb964e4 100644
--- a/a_scanner_darkly/main.cpp
+++ b/a_scanner_darkly/main.cpp
@@ -20,11 +20,12 @@ int main(int argc, char** argv ) {
 	cv::createTrackbar(LOWER_THRESHOLD_TRACKBAR_NAME, WINDOW_NAME, &g_Canny_lower_threshold, 1000, NULL);
 	cv::createTrackbar(UPPER_THRESHOLD_TRACKBAR_NAME, WINDOW_NAME, &g_Canny_upper_threshold, 1000, NULL);
 
-	cv::Mat frame, cannyFrame;
+	cv::Mat frame, grayscaleFrame, cannyFrame;
 	while (true) {
 		cap >> frame;
 
-		cv::Canny(frame, cannyFrame, g_Canny_lower_threshold, g_Canny_upper_threshold);
+		cv::cvtColor(frame, grayscaleFrame, cv::COLOR_BGR2GRAY);
+		cv::Canny(grayscaleFrame, cannyFrame, g_Canny_lower_threshold, g_Canny_upper_threshold);
 
 		cv::imshow(WINDOW_NAME, cannyFrame);