diff --git a/posts/2016-10-04-pi-pan-tilt-2.md b/posts/2016-10-04-pi-pan-tilt-2.md
index 011cac6..62b2057 100644
--- a/posts/2016-10-04-pi-pan-tilt-2.md
+++ b/posts/2016-10-04-pi-pan-tilt-2.md
@@ -102,9 +102,13 @@ calculated:
 [![Hugin comparison](../assets_external/2016-10-04-pi-pan-tilt-2/hugin-comparison.png){width=100%}](../assets_external/2016-10-04-pi-pan-tilt-2/hugin-comparison.png)
 
 They sort of match up, though pitch deviates a bit.  I believe that's
-because I shifted the pitch of the entire thing to straighten it out
-(or perhaps it did this automatically to center it), but I haven't
-examined this in detail yet.
+because I shifted the pitch of the entire thing to straighten it out,
+or perhaps Hugin did this automatically to center it, but I haven't
+examined this in detail yet.  (Helpfully, the same process can be used
+to [calibrate lenses][hugin_lens] and compute the real focal length at
+the same time - which can be particularly necessary for cases like
+this where I'm trying to get the most out of cheap optics and when the
+Exif tags won't include focal lengths.)
 
 A full-resolution JPEG of the result (after automated stitching,
 exposure fusion, lens correction, and so on), is linked below:
@@ -141,3 +145,4 @@ images!
 [pto]: http://hugin.sourceforge.net/docs/manual/PTOptimizer.html
 [pto_gen]: http://wiki.panotools.org/Pto_gen
 [pto_var]: http://wiki.panotools.org/Pto_var
+[hugin_lens]: http://hugin.sourceforge.net/tutorials/calibration/en.shtml