Aerial stereo - part 2

[P3D <PTWW@xxxxxxx>]

Over the past two weeks I have received from the processor several more
rolls of slides from my travel binge this fall.  I previously mentioned
flying over the Grand Canyon and some of the National Parks in Southern
Utah.  That was on my flight from Phoenix to Seattle (which had a stop
in Portland inserted by the airline *after* I bought the non-refundable
ticket!).  While flying over Utah, I finished the roll of film I had
started on the ground at the Grand Canyon, then put the camera away
without reloading it.  What a terrible lack of forethought!  I had
totally failed to think ahead to the beautiful scenery that would be
visible from the air at the other end of the flight!  As we proceeded
to make a close pass by Oregon's Mt. Hood, I belatedly came to my senses.
By the time I retrieved the camera and reloaded, the plane had turned
for approach into Portland, and the (morning time) view out my window
was toward the south instead of the west, presenting a difficult lighting
situation.  I shot a stereo pair of a somewhat hazy scene of a mountain
range with two snow-capped volcanoes, one in mid-ground and one in the
background.  The "bad" lighting, morning fog/haze, and patterns of the
mountain range combined to create something of a mystical feeling in
the image captured on film, which I actually found quite pleasing.
The irony is that the bad lighting normally would have caused me to
pass on the shot, but because I had missed a (very different) shot
with "good" lighting, I wanted to "at least get something."  (Not to
mention the fact that I never would have seen this particular view if
the plane had flown non-stop to Seattle like I expected when I bought
the ticket.)  Many people ask me if they are looking at water when
they view this stereo image.  The miniaturization effect of the hyper
view does make the mountains look somewhat like large waves on water.

On the way to Seattle after the unexpected stop in Portland, I was able
to shoot some pairs of Mt. Rainier.  I was surprised and disappointed
that the pair with just the volcano was not particularly interesting in
a 3-D sense.  However, a shot taken at a wider zoom setting with Mt.
St. Helens in the foreground and Rainier in the background proved much
more worthwhile.  There was some interference from long thin clouds
that partially obscure the Mt. St. Helens crater and may be somewhat
"off" stereoscopically, but at the same time these clouds add some very
powerful 3D sensations to the image.

When we left Seattle I was able to snap a shot of some peaks on the
Olympic peninsula, and one or two of some mountains in northern Calif.
But the most memorable shot from that flight is of the Golden Gate
Bridge, taken on approach into the Oakland airport.  There were of
course boats moving on the water, but from the air they are small
enough that their movement between the two images doesn't bother me
at all.

By the time I flew into Anchorage, a new idea had dawned on me (which
I later also read about when I finally discovered the FAQ in HTML format
on the Rocky Mountain Memories web site.)  Instead of merely shooting
two shots of each scene, I shot four so I could experience the effect
of a different stereo base used on the same scene.  This is very easy
to do with twin 2x2s and a cheapo twin 2x2 viewer from Reel3D.  I was
on the left side of the plane, so I successively view shots 1&2, 1&3,
1&4, then back to 1&2.  This is quite educational!  We were flying over
a spectacular view of permanent ice fields cradled by jagged mountains
with glaciers spilling over the edges, a mountain lake and an ocean
inlet.  So far I have not been able to successfully verbalize for my
wife an explanation of the differences among the images perceived when
viewing the different pairs.  Before attempting to do so, I asked her
if she could see any difference.  Her comment surprised me.  She said
the level of the water in the lake changed!  Now I knew the water level
didn't change, so I said let me see that again!  Of course what is
happening is that as the stereo base increases, the mountains (and
everything else) appear smaller.  I am guessing her perspective was
"Now I know the mountains didn't shrink!" so her brain explained the
visual disparity by supposing that in the more-hyper view, more of
the mountains were just submerged under water.  So when viewing images
1&4, the basin formed by the mountains appears very full of water, but
when viewing images 1&2 the basin appears not very full at all.  As I
mentioned, my attempt to explain to her the hyperstereo effect was not
at all successful; and she could not accept my assertion that there
was also a compression of depth in the foreground to background axis.

Flying back from Alaska, the pilot announced that there was a good
view of the northern lights...but out of the wrong (for me) side of
the plane.  The flight was extremely full, so I was unable to even
catch a glimpse of the view!  I suspect the length of exposure required
to capture them on film, with the motion of the plane, would have made
for wholly unsuccessful stereo, however.  Has anyone on the list made
stereo images of the northern lights from the ground?

On the way back home from Seattle, I again had a chance to shoot a
volcano in either southern Washington or northern Oregon.  Although
the image is mostly of the volcano, it seems a much better success
stereoscopically than my shot of Mt. Rainier.  My wife says it looks
like we are about to fly right into the mountain!  Especially because
swapping out the second image affects the perception of the height
from which the image was taken and the distance to the volcano.
Because the apparent height and depth change when going from one
pair combination to another, it does seem to give the impression
that we were flying toward the mountain instead of flying past it!

Later in that flight, we flew over what I think was the Rocky Mountains
in Colorado.  The lighting was less than ideal and I also feared that the
image was not going to be especially interesting.  However, the hyper
effect captures a lot more depth than I recall noticing as we flew over
the scene, so the stereo shot turned out to be very nice after all.

Apart from the shot of the Golden Gate Bridge, I made only one other
attempt to photograph any man-made objects from the air, and it was
quite a flop.  At Dr. T's urging I did also shoot one stereo pair of
clouds from the plane, but it really didn't do anything for me.  The
cloud scene I had to work with was probably not a very good one.  I'm
sure that Dr. T has many striking pictures of clouds in 3D, but I do
not have any!

In summary, experimenting with aerial hypers has been a thoroughly
rewarding experience for me.  I highly recommend that all P3Ders give it
a try, especially if you have the opportunity to fly over the western
US or other places with sizable natural features.  And once again I
thank Tom Dory for his timely comment in praise of John Weiler's fine
work with aerial stereo, and of course also John himself for including
his images in the expo (which I've heard about but haven't seen.)

Paul Talbot


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