diff --git a/gopro_8:7/unfish_gopro_8:7.glsl b/gopro_8:7/unfish_gopro_8:7.glsl
index b86fb72..b2334fa 100644
--- a/gopro_8:7/unfish_gopro_8:7.glsl
+++ b/gopro_8:7/unfish_gopro_8:7.glsl
@@ -33,8 +33,8 @@ uniform float pts;
 
 // parameters
 const vec2 sensor_size = vec2(5.949440, 5.205760);
-const float equidistant_focal_length = 3.020000;
-const float rectilinear_focal_length = 2.232346;
+const float equidistant_focal_length = 2.970000;
+const float rectilinear_focal_length = 2.167601;
 
 // constants
 const int subsampling = 4;
diff --git a/gopro_8:7/unfish_gopro_8:7.py b/gopro_8:7/unfish_gopro_8:7.py
index e73de60..9152e69 100644
--- a/gopro_8:7/unfish_gopro_8:7.py
+++ b/gopro_8:7/unfish_gopro_8:7.py
@@ -20,39 +20,25 @@ print("\n--- physical sensor ---\n")
 
 # https://www.sony-semicon.com/files/62/pdf/p-13_IMX677-AAPH5-J_Flyer.pdf
 
-sensor_array_horizontal = 5700 # p
-sensor_array_vertical   = 5160 # p
-sensor_array_diagonal   = math.hypot(sensor_array_horizontal, sensor_array_vertical)
-
 sensor_pixel_size = 1.12 * 0.001 # mm
 
-sensor_size_horizontal = sensor_array_horizontal * sensor_pixel_size
-sensor_size_vertical   = sensor_array_vertical   * sensor_pixel_size
-sensor_size_diagonal   = math.hypot(sensor_size_horizontal, sensor_size_vertical)
-
-print("sensor size : horizontal = %7.3f, vertical = %7.3f, diagonal = %7.3f (mm)" % (
-    sensor_size_horizontal,
-    sensor_size_vertical,
-    sensor_size_diagonal))
-
 # https://community.gopro.com/s/article/HERO11-Black-Video-Settings-And-Resolutions
 
 gopro_array_horizontal = 5312 # p
 gopro_array_vertical   = 4648 # p
-gopro_array_diagonal   = math.hypot(gopro_array_horizontal, gopro_array_vertical)
 
-gopro_size_horizontal = (gopro_array_horizontal / sensor_array_horizontal) * sensor_size_horizontal
-gopro_size_vertical   = (gopro_array_vertical   / sensor_array_vertical)   * sensor_size_vertical
-gopro_size_diagonal   = (gopro_array_diagonal   / sensor_array_diagonal)   * sensor_size_diagonal
+gopro_size_horizontal = gopro_array_horizontal * sensor_pixel_size
+gopro_size_vertical   = gopro_array_vertical   * sensor_pixel_size
+gopro_size_diagonal   = math.hypot(gopro_size_horizontal, gopro_size_vertical)
 
 print("gopro  size : horizontal = %7.3f, vertical = %7.3f, diagonal = %7.3f (mm)" % (
     gopro_size_horizontal,
     gopro_size_vertical,
     gopro_size_diagonal))
 
-# https://thinglabs.io/gopro-focal-radius-guide
+# https://thinglabs.io/gopro-focal-length-guide
 
-gopro_focal_length = 3.02 # mm
+gopro_focal_length = 2.97 # mm
 
 gopro_radius_horizontal = gopro_size_horizontal * 0.5
 gopro_radius_vertical   = gopro_size_vertical   * 0.5
@@ -101,8 +87,7 @@ print("\n--- shader parameters ---\n")
 print("""// parameters
 const vec2 sensor_size = vec2(%.6f, %.6f);
 const float equidistant_focal_length = %.6f;
-const float rectilinear_focal_length = %.6f;
-""" % (
+const float rectilinear_focal_length = %.6f;""" % (
     gopro_size_horizontal, gopro_size_vertical,
     gopro_focal_length,
     rectilinear_focal_length_vertical)