Pete makes great points on resolution... my point was more to show the order
of magnitude required...And, these very thin guys aren't really meant to be
permanent, just to hold a stand-in up so that you can run around and take
pictures or have neighbors look.
For "real structural" use nobody should ever let visibility of the guy be a
Paint color is important, too, as Pete points out.. It is a bit of a trick
to find a suitable color.. what's "invisible" against the blue sky with
fluffy white clouds might not be against the setting sun, etc.
And, of course, if someone is trying to find reasons that your tower/guy
wires are ugly, then it doesn't much matter.
----- Original Message -----
From: "Pete Smith" <email@example.com>
To: "Jim Lux" <firstname.lastname@example.org>; "Mugleston, Brad"
Sent: Friday, June 20, 2003 7:16 PM
Subject: Re: [TowerTalk] Advice Requested
> At 06:49 PM 6/20/03 -0700, Jim Lux wrote:
> >Dacron fishing line works as an invisible guy... even something like
> >seine twine would probably work, and not be overly visible.
> >Human eyes can resolve about an arc minute, so you can figure out how
> >something needs to be to make it invisible, given the distance (... about
> >1/4000th of the distance, so 100 ft away, it needs to be 1/40th of a foot
> >smaller... 1/4" give or take)
> Unfortunately, this isn't the whole story. I can see the 3/16" EHS guys
> my tower from over 200 feet away. Super good eyes? Nope -- it isn't a
> matter of your eye actually being able to resolve the width of the guy
> wire, but rather the contrast between the color and/or brightness of the
> guy and the color and/or brightness of the background. The result is that
> the "pixels" through which the guy wires pass have a noticeably different
> *average* color and/or brightness than those adjacent to them, so you can
> see the wire even though it is too small to resolve.
> I didn't used to believe this until I saw 30-meter-resolution satellite
> photos of the causeway across Lake Pontchartrain that clearly showed a
> roadway whose width was much less than the system resolution.
> Bottom line is if you want it not to show, you need to match it to the
> background as well as you can. I've seen a 75-foot tower with TH7DXX that
> you had to look three times to resolve against the forest background
> because of a carefully applied coat of brown-grey paint.