diff --git a/hazenlib/tools.py b/hazenlib/tools.py
index 64e6cc02..15e9aaa9 100644
--- a/hazenlib/tools.py
+++ b/hazenlib/tools.py
@@ -66,7 +66,7 @@ def find_contours(self):
         # convert the resized image to grayscale, blur it slightly, and threshold it
         self.blurred = cv.GaussianBlur(self.arr.copy(), (5, 5), 0)    # magic numbers
 
-        optimal_threshold = filters.threshold_li(self.blurred, initial_guess=np.quantile(self.blurred, 0.25))
+        optimal_threshold = filters.threshold_li(self.blurred, initial_guess=np.quantile(self.blurred, 0.50))
         self.thresh = np.where(self.blurred > optimal_threshold, 255, 0).astype(np.uint8)
 
         # have to convert type for find contours