diff --git a/NOTES b/NOTES
index fbfa9a1..49ec8ac 100644
--- a/NOTES
+++ b/NOTES
@@ -527,3 +527,6 @@ size | area/diagonal pixel
 70   | 1+28/49 = 1.57
 90   | 1+36/81 = 1.44
 100  | 1+50/100 = 1.5
+
+So the _very_ best sizes are 20, 60, 100, etc.  90 and 50 are pretty
+good because they're between √2 and 1.5.