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Cyhist Feb 20 1997 A
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Date: Thu, 20 Feb 1997 12:32:35 -0500
Reply-To: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> Sender: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> From: Chris Chiesa <lvt-cfc@SERVTECH.COM>
Organization: LVT / Eastman Kodak Co., Inc. Subject: CM> Re: rapid arm movements
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Community Memory: Discussion List on the History of Cyberspace ______________________________________________________________________
Les Earnest <les@STEAM.STANFORD.EDU> writes
>
>Keith S. Reid-Green writes:
>[. . .]
>But I digress. Regarding Chris's arm-waving, when we got the TV I noticed that if I moved my hand quickly in front of the set I could detect the screen blanking. This was because I would see two or three silhouettes of my hand. My brother and I had contests to see who could move a yardstick the fastest, as measured by the number of yardsticks we could count as the real one passed across the screen. For the record, each instance represented 1/30 second.
>
>More likely each silhouette represented a 1/60 second interval -- the time between successive fields on NTSC television.
This is somewhat off-topic, but this reminds me of something else. My Dad
was a professional photographer, and often needed to know a camera's "actual"
shutter speed -- as opposed to "the speed it was SET to." Dad accomplished
this for shutter speeds shorter than 1/30 second by photographing television
screens and counting scanlines: 525 lines made up 1/30 second, so a shutter's
speed was 1/30 * N/525, where N was the number of scanlines included in the
resulting picture. Another method was to plug a cord with a neon bulb on it,
into the wall outlet, whirled the cord around in a vertical circle, and photo-
graph this exercise. The neon bulb went on and off every 1/60 second, and you
just counted the number of bulb-images you got, around the partial circle that
appeared in the photograph.
A little more on-topic, to preserve the readability of this message... I've
noticed recently that people are dumping VAXstations like crazy all of a sud-
den. After wanting "a VAX of my own" for ten years or so, but being unwilling
and unable to pay hundreds, or thousands, of dollars for the privilege, in the
last week I've been offered THREE 3200 MicroVAXes for NOTHING. I'm taking two
of them... :-) "When it rains, it pours!"
Chris Chiesa
lvt-cfc@servtech.com
______________________________________________________________________
Reply-To: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> Sender: "CYHIST Community Memory: Discussion list on the History of
Cyberspace" <CYHIST@MAELSTROM.STJOHNS.EDU> From: Chris Chiesa <lvt-cfc@SERVTECH.COM>
Organization: LVT / Eastman Kodak Co., Inc. Subject: CM> Re: rapid arm movements
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit
______________________________________________________________________
Community Memory: Discussion List on the History of Cyberspace ______________________________________________________________________
Les Earnest <les@STEAM.STANFORD.EDU> writes
>
>Keith S. Reid-Green writes:
>[. . .]
>But I digress. Regarding Chris's arm-waving, when we got the TV I noticed that if I moved my hand quickly in front of the set I could detect the screen blanking. This was because I would see two or three silhouettes of my hand. My brother and I had contests to see who could move a yardstick the fastest, as measured by the number of yardsticks we could count as the real one passed across the screen. For the record, each instance represented 1/30 second.
>
>More likely each silhouette represented a 1/60 second interval -- the time between successive fields on NTSC television.
This is somewhat off-topic, but this reminds me of something else. My Dad
was a professional photographer, and often needed to know a camera's "actual"
shutter speed -- as opposed to "the speed it was SET to." Dad accomplished
this for shutter speeds shorter than 1/30 second by photographing television
screens and counting scanlines: 525 lines made up 1/30 second, so a shutter's
speed was 1/30 * N/525, where N was the number of scanlines included in the
resulting picture. Another method was to plug a cord with a neon bulb on it,
into the wall outlet, whirled the cord around in a vertical circle, and photo-
graph this exercise. The neon bulb went on and off every 1/60 second, and you
just counted the number of bulb-images you got, around the partial circle that
appeared in the photograph.
A little more on-topic, to preserve the readability of this message... I've
noticed recently that people are dumping VAXstations like crazy all of a sud-
den. After wanting "a VAX of my own" for ten years or so, but being unwilling
and unable to pay hundreds, or thousands, of dollars for the privilege, in the
last week I've been offered THREE 3200 MicroVAXes for NOTHING. I'm taking two
of them... :-) "When it rains, it pours!"
Chris Chiesa
lvt-cfc@servtech.com
______________________________________________________________________
