diff --git a/datasets/raise/extract_noise.py b/datasets/raise/extract_noise.py
index 429e03d..21491b5 100755
--- a/datasets/raise/extract_noise.py
+++ b/datasets/raise/extract_noise.py
@@ -125,15 +125,16 @@ def treatImage(imageFileName, computeExtremes = False, color = None):
         mean = ((mean * numberOfImagesInMean) + imageNoiseNpArray) / (numberOfImagesInMean + 1)
     numberOfImagesInMean += 1
 
-# Assuming same intensity scale across color channels.
-for imageFileName in tqdm(imagesFileNames, 'Computing extremes of images'):
-    for color in colors:
-        treatImage(imageFileName, computeExtremes = True, color = color)
+if minColor is None or maxColor is None:
+    # Assuming same intensity scale across color channels.
+    for imageFileName in tqdm(imagesFileNames, 'Computing extremes of images'):
+        for color in colors:
+            treatImage(imageFileName, computeExtremes = True, color = color)
 
-# To skip this step next time.
-# Maybe thanks to `rawpy.RawPy` fields, possibly stating device maximal value, can avoid doing so to some extent.
-print(f'{minColor=}')
-print(f'{maxColor=}')
+    # To skip this step next time.
+    # Maybe thanks to `rawpy.RawPy` fields, possibly stating device maximal value, can avoid doing so to some extent.
+    print(f'{minColor=}')
+    print(f'{maxColor=}')
 
 if denoiser == 'mean':
     means = {}