Re: [photo-3d] Hyperstereo from airliner - frame rate?

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

----- Original Message -----
From: "Roger Loper" <roger@xxxxxxxxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Tuesday, January 09, 2001 10:24 AM
Subject: Re: [photo-3d] Hyperstereo from airliner - frame rate?


>
>
> William Gartin wrote:
>
> > A while back there was reference to taking hyperstereo from an airplane
> > using a motordrive. I was wondering what a typical time between frames
might
> > be. Do you space them out, say a second apart, or do you just fire off a
few
> > frames in continuous mode? I'm using a Nikon FM/MD-12 which runs around
> > 3fps, if that helps. I'd really like to try this the next time I fly.
>
> Before I submit my comments to this post, let me introduce myself since
I'm new
> to the list.  My name is Roger and I live in a log cabin in the mountains
in
> Western Colorado.  I bought my first stereo camera (a Realist 3.5) in 1963
from
> a pawn shop.  I've really enjoyed reading the posts for the last several
days
> and it's great finding such a knowledgable group that shares my passion
for
> stereo photography.
>
> Now to the subject of hyperstereo from aircraft...  The government takes a
lot
> of these pictures.  They use a high resolution camera mounted in the belly
of
> the plane.  The US Geological Survey uses them for generating topographic
maps
> and the Forest Service uses them for making timber counts.  I used to buy
them
> and carry them on backpacking trips.  I'd free-view them and could often
glean
> details about the terrain that weren't apparent from the topographic maps.
The
> photos I have use a very wide stereo base--about a third of the total span
of
> the photo.  This gives exaggerated stereo, but is quite impressive.  These
> pictures were taken, of course, with the camera pointed straight down.
I've
> never experimented with taking my own from a commercial airliner, but I
would
> think that one would want to wait at least several seconds between shots.
> Assume that you're flying at 30,000 feet and going about 700 feet per
second
> (about 500 MPH).  Different lenses would give different picture widths,
but
> assume that you can see about 30,000 feet on the ground.  To have a third
of the
> picture go buy would take about 14 seconds, but this would give the
exaggerated
> stereo effect I mentioned.  I'd think around 5 seconds would be a good
starting
> point.
>
> Now, I have a question.  I recently purchases a TDC 716A projector on
eBay.
> Everything seems fine except for one very serious problem.  If I get one
lens in
> focus, the other one isn't.  I could probably tear into it and find out if
there
> is a way internally to adust the focus of the lenses independently, but
one of
> you out there probably could save me some grief.  HELP!!!
>
> Roger
>
Welcome to the group!   Your aerial comments are right on (I sent a similar
on post a while ago).

With my 716, I first set the normal focus knob to about the middle of the
range, and then focus each lens individually (they are threaded).  Then they
will track each other when focusing normally with the knob.   You normally
have to do this only once, unless somebody turns the lenses, or you change
them (as for another focal length).

JR