Author Topic: Stereo parallax  (Read 30815 times)

Offline Kiwi

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Re: Stereo parallax
« Reply #15 on: September 21, 2014, 10:31:36 AM »
...Not freaking full-motion video from a rover as it rides for twenty minutes at a time across the landscape!)

Small correction -- that's colour movie film that we see taken from the rover when it's in motion, and it often shows the video camera which was always stowed for trips between stations, mainly because the antenna had to be accurately aimed at earth for the video to be transmitted successfully.

One thing you've not mentioned is the multitude of photos taken by the LMP when travelling between stations. In many cases distant rocks can be seen, along with more photos as the rover approaches them. Apollo 17's Turning Point Rock and Tracy's Rock are just two of many examples, and sometimes video or stills can be seen looking back at the route taken and showing the rover's tracks.

There are three types of things that I think have been underused in debunkings of the "filmed in a studio" claims:--

1. The long video clips taken on the EVAs from the Apollo 16 and 17 rovers.  They don't always concentrate on the astronauts and include pans and tilts up, down and around, and they never show any sort of studio environment. No furniture, reflectors, artificial lights, power cords, stands, gantries, or cranes. And most vehicle tracks and footprints can be attributed to either the activities we see or to activities that were otherwise documented.

2.  Long-distance photos or video of the lunar module, which included telephoto shots of the LM from a distance, or wide-angle shots that accidentally included it, such as the panoramas at Tracy's Rock (or Split Rock) at Apollo 17's Station 6, which include a tiny LM in the distance to the right of the top of the rock -- see AS17-140-21493 to 21496.
http://www.hq.nasa.gov/alsj/a17/AS17-140-21493HR.jpg
http://www.hq.nasa.gov/alsj/a17/AS17-140-21494HR.jpg
http://www.hq.nasa.gov/alsj/a17/AS17-140-21495HR.jpg
http://www.hq.nasa.gov/alsj/a17/AS17-140-21496HR.jpg

On the other hand, there are photos that include Tracy's Rock or Turning Point Rock from the vicinity of the LM or the ALSEP site, and there's the upsun video of Jack Schmitt skipping back to the LM when he sings "I was strolling on the moon one day..."

HBs would have trouble describing a realistic studio and setup for the Apollo 16 Grand Prix.

3. Video of astronauts taking panoramas and telephoto shots. For instance, Gene Cernan is on video taking a series of telephotos shots of one of the massifs from close to the rover, and we can see a slight motion of the lens as he presses the shutter. We can also examine the photos he took, and some of them show camera shake because of that lens motion.
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Offline gillianren

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Re: Stereo parallax
« Reply #16 on: September 21, 2014, 11:10:24 AM »
Absolutely! What makes me laugh is when they try to use Capricorn One as an example of how the pictures could have been faked, when the Mars shots in that film consist of one tiny, tightly-framed set, around which the camera doesn't move!

When I saw the movie, my opinion was that the set was even too small for a TV show.  You'd have to have been extremely careful in every shot not to get the edges of the backdrop.  It was one of the (many) problems I had with that movie.
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Offline AstroBrant

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Re: Stereo parallax
« Reply #17 on: September 21, 2014, 09:56:01 PM »
(snip...)
Is that the distortion info in this document?:
https://www.hq.nasa.gov/alsj/Biogon5.6_60mm_ZEISS.pdf

Yes, that's it. I could get the general idea but not enough to tackle Oleynik's analysis. thank you for the rest of the information. I may be able to figure it out now, but it seems that the distortions I am seeing are way outside of those specs. maybe there's another reason for it.

One thing I have found for my critique is a stereo pair of pictures taken from the same place, showing significant distortion. The background stretches considerably from one picture to the next, both vertically and horizontally. This would be good for making the point that it must be something other than true parallax that we are seeing since the baseline is of negligible length.
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Offline AstroBrant

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Re: Stereo parallax
« Reply #18 on: September 21, 2014, 10:05:38 PM »


One thing you've not mentioned is the multitude of photos taken by the LMP when travelling between stations.

Yes, especially in Apollo17. I used about 20 or 30 in sequence in one of my videos, all centered on the western peak of South Massif. IIRC there were over a hundred pics from one traverse.

Re. Grand Prix. Another tough one to pass off as a studio shot is Jack carrying the ALSEP equipment out. He disappears completely from sight over one ridge.
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Offline nomuse

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Re: Stereo parallax
« Reply #19 on: September 21, 2014, 10:31:41 PM »
The clip I remember is...I think it was "House Rock," but I can't remember the flight. Shot from the parked rover, the astronauts go walking down a gentle slope towards a boulder. And keep walking. And keep walking. Because the boulder is the size of a small house. And if you are imagining a studio shot, the size of that studio gets larger, and larger, and larger as they walk.

Offline cjameshuff

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Re: Stereo parallax
« Reply #20 on: September 21, 2014, 11:37:52 PM »
The clip I remember is...I think it was "House Rock," but I can't remember the flight. Shot from the parked rover, the astronauts go walking down a gentle slope towards a boulder. And keep walking. And keep walking. Because the boulder is the size of a small house. And if you are imagining a studio shot, the size of that studio gets larger, and larger, and larger as they walk.


https://www.hq.nasa.gov/alsj/a16/a16.house_rock.html

Offline ka9q

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Re: Stereo parallax
« Reply #21 on: September 22, 2014, 02:24:27 AM »
Can anybody explain lens geometry to me? I know the Biogon lenses were good, but I don't know what model is considered ideal. Any lens maps (part of) a spherical scene onto a flat imaging surface, so for all of a wide-angle image of a scene at a given distance to be in focus the effective focal length of the lens has to be greater at the edges of the image. That implies that a given angular separation will appear larger on the flat film at the edges of the image than at the center.

Am I right that it's this simple? Or does the lens do more?
« Last Edit: September 22, 2014, 02:26:44 AM by ka9q »

Offline cjameshuff

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Re: Stereo parallax
« Reply #22 on: September 22, 2014, 07:44:52 AM »
Can anybody explain lens geometry to me? I know the Biogon lenses were good, but I don't know what model is considered ideal. Any lens maps (part of) a spherical scene onto a flat imaging surface, so for all of a wide-angle image of a scene at a given distance to be in focus the effective focal length of the lens has to be greater at the edges of the image. That implies that a given angular separation will appear larger on the flat film at the edges of the image than at the center.

Am I right that it's this simple? Or does the lens do more?

There are many different ways to do it, just as there's many ways of projecting a globe onto a flat map. Most lenses try to imitate a pinhole camera, which behaves as you describe, keeping lines straight but having angular sizes exaggerated away from the center. Other lenses are designed to preserve angular size or area, and will produce curved images of straight lines, but tend to be better suited to wide angles.

http://en.wikipedia.org/wiki/Fisheye_lens#Mapping_function

And of course, real lenses have to work with a light field manipulated through a series of lenses and can only approximate these.

Offline JayUtah

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Re: Stereo parallax
« Reply #23 on: September 22, 2014, 07:39:13 PM »
Can anybody explain lens geometry to me? I know the Biogon lenses were good, but I don't know what model is considered ideal. Any lens maps (part of) a spherical scene onto a flat imaging surface, so for all of a wide-angle image of a scene at a given distance to be in focus the effective focal length of the lens has to be greater at the edges of the image. That implies that a given angular separation will appear larger on the flat film at the edges of the image than at the center.

Am I right that it's this simple? Or does the lens do more?

The Biogon lens tried to more faithfully replicate life by pushing the most notable distortion toward the edges of the frame -- mostly in the corners.
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Offline AstroBrant

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Re: Stereo parallax
« Reply #24 on: September 23, 2014, 01:32:34 AM »
The clip I remember is...I think it was "House Rock," but I can't remember the flight. Shot from the parked rover, the astronauts go walking down a gentle slope towards a boulder. And keep walking. And keep walking. Because the boulder is the size of a small house. And if you are imagining a studio shot, the size of that studio gets larger, and larger, and larger as they walk.

That one was an excellent demonstration of how deceiving size and distance can be on the moon. One of the several videos I would like to make is one which would show lunar scenes and ask the viewer to guess how far away or how big certain features are. I've already done some of the calculations and have images that I have added objects to, like an aircraft carrier, a school bus, and the New York city skyline.

That House Rock clip will be in my video. I also have some pictures from a rover traverse sequence where two rocks seem to be about the same size and at about the same distance. The next few frames will show us approaching and passing one of the rocks while the other is still a long way off.
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Offline nomuse

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Re: Stereo parallax
« Reply #25 on: September 23, 2014, 03:17:44 AM »
Not completely restricted to the Moon. I had the experience of walking along the floor of Death Valley. No plants, nothing to take scale off of, extremely dry air and little in the way of aerial perspective. I could still get a general sense of how far it was to the rock formation I was heading for, but only within a magnitude (I guessed almost that low!)

Offline ka9q

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Re: Stereo parallax
« Reply #26 on: September 23, 2014, 04:05:12 AM »
That one was an excellent demonstration of how deceiving size and distance can be on the moon. One of the several videos I would like to make is one which would show lunar scenes and ask the viewer to guess how far away or how big certain features are. I've already done some of the calculations and have images that I have added objects to, like an aircraft carrier, a school bus, and the New York city skyline.
Have you seen the IMAX film Magnificent Desolation? Tom Hanks, who narrated, did something very similar with images from my favorite Apollo mission, Apollo 15. It's my favorite because of the dazzling scenery, especially Hadley Rille. To make this point about scale, he stuck the Statue of Liberty to scale down in the rille.

It wasn't just us looking at TV and photos who had trouble judging scale on the moon. The astronauts themselves were often fooled.


Offline AstroBrant

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Re: Stereo parallax
« Reply #27 on: September 30, 2014, 10:35:58 PM »
(snip...)
Have you seen the IMAX film Magnificent Desolation? Tom Hanks, who narrated, did something very similar with images from my favorite Apollo mission, Apollo 15. It's my favorite because of the dazzling scenery, especially Hadley Rille. To make this point about scale, he stuck the Statue of Liberty to scale down in the rille.

It wasn't just us looking at TV and photos who had trouble judging scale on the moon. The astronauts themselves were often fooled.

No, I haven't seen it. I'll have to check it out. Darn! Every time I think I have an original idea for something I find out somebody else already did it. Oh well, at least I'll know not to use the Statue of Liberty.

On this matter of parallax measurement and lens distortion I noticed something just a couple of days ago. I found pictures of the earth taken by Gene from Station 2, (near Nansen, at the base of South Massif). He did a pan from the same place. I thought it would be fun to make my own pan and add the earth above it. I just used MS Paint, but I was amazed at how badly some of the pictures lined up. Some of this could be attributed to the changing of the vertical angle of the camera from one picture to the next, but there were other problems, like how vertical distances between two objects near the right edge of one picture were quite different from their separation as they appeared near the left edge of the next picture. These must be caused by lens distortion. Since they are the same objects and the pictures were taken from the same spot, it couldn't be due to parallax or perspective foreshortening.

I wonder if the people who have assembled pans for ALSJ run into this problem so much that it becomes a matter of routine for them, and if they have to skew pictures to make objects line up where they join them together. I wonder if they even may have to vertically compress the top portion of some pictures and stretch the bottom, and vice versa.
 
This may be a good point in my video.
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Offline ka9q

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Re: Stereo parallax
« Reply #28 on: October 01, 2014, 06:15:01 AM »
I can't really speak to the topic of lens distortion, but I know there are programs that will assemble panoramas for you while correcting for geometric distortion and/or remapping the composite image to a different projection.

Regarding visual size comparisons for Hadley Rille, an obvious one that I haven't actually seen yet is to put it and the Grand Canyon either side-by-side or on top of each other to proper scale, of course. You would have to find a picture of the Canyon with a similar perspective to one of Apollo 15's shots of the Rille. We visited the Canyon two years ago and took tons of pictures from both North and South Rim I'd be willing to contribute.



Offline Zakalwe

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Re: Stereo parallax
« Reply #29 on: October 01, 2014, 01:02:50 PM »
I can't really speak to the topic of lens distortion, but I know there are programs that will assemble panoramas for you while correcting for geometric distortion and/or remapping the composite image to a different projection.



There's plenty of stitching programs out there. Photosynth is very good, as is the free Microsoft Image Composite Editor.
http://research.microsoft.com/en-us/um/redmond/groups/ivm/ice/
https://photosynth.net/

Photoshop also does a very good job (use the Photomerge tool).
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