Minor doc change

skimage/feature/orb.py

@@ -48,7 +48,8 @@ def keypoints_orb(image, n_keypoints=500, fast_n=9, fast_threshold=0.08,
         separate corners from edges, typically in range ``[0, 0.2]``. Small
         values of k result in detection of sharp corners.
     downscale : float
-        Downscale factor for the image pyramid.
+        Downscale factor for the image pyramid. Default value 1.2 is chosen so
+        that we have more scales per octave i.e. log1.2(2) in this case.
     n_scales : int
         Number of scales from the bottom of the image pyramid to extract
         the features from.

skimage/feature/util.py

@@ -1,6 +1,6 @@
 import numpy as np
 
-from ..util import img_as_float
+from skimage.util import img_as_float
 
 
 def _prepare_grayscale_input_2D(image):