[Top] [All Lists]

[TowerTalk] Acuity

To: <>
Subject: [TowerTalk] Acuity
From: (George Cutsogeorge)
Date: Thu, 18 Mar 1999 16:35:22 -0800

The same discussion appears in the Television Engineering
Handbook edited by Fink.  I quote: "For visual acuity tests of
the type described, normal vision, corresponding to a Snellen
20/20 rating, represents an angular discrimination of about 1

Your friend has taken the 1 minute number and calculated how far
away you must be from a 3/16" diameter wire for it to subtend 1
minute of arc.  The answer is the 53+ feet.

Now the type of test they are talking about is the tv test patern
wedge where the lines get smaller as they converge.  The
parameter of interest is resolution.  This is not he same as
looking at a single guy wire against a blue sky.

As an example, I am looking at my 3/16" guys over 300 feet away
and they are very distinct against the sky.  If there were 10 of
them spaced 3/16" apart, it would be a different thing to try and
count them.

Next time I walk my dog I'll check how far away the guys are


-----Original Message-----
From: Fred Hopengarten <>
To: <>
To: <>
Date: Thursday, March 18, 1999 7:12 AM
Subject: [TowerTalk] Acuity

>Fred Hopengarten  K1VR               781/259-0088
>Six Willarch Road
>Lincoln, MA 01773-5105
>permanent e-mail address:
>if sending attachments:
> I had a client who took a whole new approach to the visibility
>towers issue.  Unfortunately, he recently died -- of reasons
unrelated to
>the stress of applying for a tower (which I secured).  We never
had to
>fight the fight for which we were preparing, so I never got my
hands on
>the original material.  However, here's what he wrote:
To: <>
>Date: Wed, 17 Jun 1998 23:00:15 +0000
>Subject: Guy Wires
>Dear Fred, 3/16 diameter guy wires become invisible at 54
>feet (53.6 ft).   "Principles of Television
>Engineering", D.G. Fink, McGraw-Hill, 1940, p. 32.
>Apparently this book has a formula in it which discusses acuity
of the
>human eye. Does anyone here have the book? Or a similar formula?
>doesn't help when you neighbor gets upset, but it does help when
>says:  "I'll be able to see it from clear across the bay."
>I suspect that anyone who works on TV, computer monitors, or who
is an
>optometrist or opthalmologist, might be able to contribute to
>question:  At what distance does a thin object disappear to the
>-- Fred K1VR
>You don't need to buy Internet access to use free Internet
>Get completely free e-mail from Juno at
>or call Juno at (800) 654-JUNO [654-5866]
>FAQ on WWW:
>Administrative requests:

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>