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Ultimate digital vs film: 1gp digital vs SR71 reconnaissance cameras



 
 
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  #1  
Old December 7th 04, 05:12 PM
daveyp225
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Default Ultimate digital vs film: 1gp digital vs SR71 reconnaissance cameras


jjs wrote:
"Judson McClendon" wrote in message
...

Take those declassified documents with a grain of salt.


I saw declassified satellite images around 1960 where you could
read the logo on the side of a truck. [...]


Mind if I Laugh Out Loud? If they (whomever 'they' are) said those

were
satellite images, then it was pure misinformation and served its

purpose in
that regard: you were fooled, and it may have frightened the Soviets

into
further spending themselves to oblivion.



I believe him. Have you ever heard of teraserver? It is a satelite
available to the public which can basically see your backyard. If such
tech is available to regular citizens now, dont you think the military
has at least that back then? I wouldn't be surprised if the military
can get your shirt size from satelites now.

  #2  
Old December 7th 04, 11:18 PM
jjs
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"daveyp225" wrote in message
oups.com...

jjs wrote:
"Judson McClendon" wrote in message
...

Take those declassified documents with a grain of salt.


I saw declassified satellite images around 1960 where you could
read the logo on the side of a truck. [...]


Mind if I Laugh Out Loud? If they (whomever 'they' are) said those

were
satellite images, then it was pure misinformation [...]


I believe him. Have you ever heard of teraserver? It is a satelite
available to the public which can basically see your backyard. If such
tech is available to regular citizens now, dont you think the military
has at least that back then? I wouldn't be surprised if the military
can get your shirt size from satelites now.


I will let Hemi give the optical metrics required to resolve a "logo on the
side of a truck", or license plate, or any image with angular requisites
from a sattelite. Remember, back in the sixties they actually had to drop
the film magazines from space to be caught by aircraft with tailhooks. I
truly doubt teraserver's technology uses 60's tech.


  #3  
Old December 7th 04, 11:40 PM
Hemi4268
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I will let Hemi give the optical metrics required to resolve a "logo on the
side of a truck"


Well, if you get in top of a high bridge looking over a major highway, you will
not be able to see any logos on sides of trucks. Although, you will be able
to see any logos on top of the truck.

Same with licence plates. The licence plates must be looking up so you can
read them looking down.

As soon as someone says they can see licence plates from so many miles up I
laugh. Licence plates are designed to be read from the road and not from the
sky. Same with logos on the sides of trucks.

Larry
  #4  
Old December 8th 04, 03:03 AM
jjs
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Hemi:

Do you think there are any government sixties or seventys recon lenses we
cannot purchase surplus?


  #5  
Old December 8th 04, 03:54 AM
Hemi4268
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Hi

You might find one but they are designed to be used in a scan mode much like a
strip camera is used at a horse race track.

The film passes a small slit in sync with the ground speed. Exposure is by the
slit width. Example, a 1 inch slit with the film going 12 inches a second
gives 1/12 of a second exposure. If the reduction is 1000 to 1 then the camera
would be traveling 1000 feet per second over the target. Add a few zeros and
it's all the same ratio. So 10000 to 1 reduction is 10000 feet per second and
100000 to 1 reduction is 100000 feet per second.

A 1/2 inch slit would be 1/24 of a second, 1/4 inch is 1/48 of a second and 1/8
inch would be 1/92 of a second and so on and so on.

Larry


  #6  
Old December 8th 04, 05:29 AM
jjs
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"Hemi4268" wrote in message
...

You might find one but they are designed to be used in a scan mode much
like a
strip camera is used at a horse race track.
[... snip good stuff ...]


Yes, I remember those monsters, but you know there were a couple that did
not use slits or FP shutters, usually short lenses behind a heated port.
Remember? It has been a long time.


  #7  
Old December 8th 04, 10:53 AM
Jim Phelps
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"jjs" wrote in message
...
Hemi:

Do you think there are any government sixties or seventys recon lenses we
cannot purchase surplus?


Satellite - No, they all burned up upon reentry.

Aircraft - Possible, check your local DMRO at a military base near you.


  #8  
Old December 8th 04, 11:06 AM
Jim Phelps
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"jjs" wrote in message
...
I will let Hemi give the optical metrics required to resolve a "logo on
the side of a truck", or license plate, or any image with angular
requisites from a sattelite. Remember, back in the sixties they actually
had to drop the film magazines from space to be caught by aircraft with
tailhooks. I truly doubt teraserver's technology uses 60's tech.


Don't forget the advantages of having those optics in a vacuum and the path
from subject to optic is influenced by an ever decreasing proportion of
atmospheric interference.


  #9  
Old December 8th 04, 06:08 PM
columbotrek
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The film used in the SR71 looks like a large format roll film. Plus the
huge diameter lens is truly impressive looking. There must be a good
reason for wanting lots of film area when resolution is of prime importance.
  #10  
Old December 8th 04, 08:44 PM
Hemi4268
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Yes, I remember those monsters, but you know there were a couple that did
not use slits or FP shutters, usually short lenses behind a heated port.
Remember?


All had heated ports although some ports were better then others. Yes your
talking about TOC cameras. I think they had 60 inch lenses. Image motion was a
big problem with these because of the single exposure vs scan.

Larry
 




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