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Message: <blockquote data-quote="elkcub" data-source="post: 1479463" data-attributes="member: 14473">I really have no problem holding a 10x25 steady, particularly since adopting the thumbs-up (military) hold.  The instrument is quite light, and has a twilight factor of 250^.5 = 15.8, which is almost identical to a standard 8x32, i.e., 256^.5= 16.  The more diminutive 8x20, however, only has a factor of 120^.5 = 12.6., making it less effective under low light conditions.  So, my choice is an 10x25, which I enjoy in the form of my trusty Swaro SLC (my wife preferring her 8x20 SLC).  But other people like different brands, and I might even spring for a Leica or Zeiss if I were buying today.  After trying one, however, I don't much care for the 10x25 LX L.  Anticipating some disagreement about the meaning or importance of Twilight Factor, the theoretical issue was settled for me some time ago by Vukobratovich (1989).  I've attached his interesting paper for  convenience.  (See pgs. 339-40, Eq. 5.)-ed</blockquote>