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Stereo images |
Site map |
Email the author |
Copyleft information |
Detta dokument på svenska |
| Last updated: March 17, 2001 | Unless otherwise specified; text, tables, photographs, maps and other graphics © 1999-2001 Gunnar Ljungstrand | |||||
Of course three dimensions is better than two, so here is some Stereo images. How do we see three-dimensionally anyway? Since the eyes are set some 7 cm from each other they see objects from somewhat different angles. Close one of your eyes, and then the other one, and you see close objects "move" in relation to more distant ones. This effect is called Parallax and gets weaker as the distance increases; therefore we only see three-dimensionally (well) within some 25 m.
Thus, to create three-dimensional images you must force the eyes to see different images. The best way of doing this is by a Hologram, where the pattern the reflected light creates depends on the viewing angle, but the technology to show such over the net does not exist yet. The most common way is Anaglyph images, one image in red and one in green/blue, and a pair of spectacles with tinted plastic for forcing the eyes to see only the intended image. These images can only be in B-W however. There are also spectacles for differently polarized light, or such ones that turn opaque a few tens of times a second, but they demand special display technology. Around the turn of the last century Stereoscopes were popular, devices where a lens system made sure the eyes only saw the intended image, and similar are still around.
What I wanted, however, was a system capable of displaying color, not requiring any kind of spectacles, that could be displayed over the net on a regular monitor, and where taking your own stereo images was simple and cheap to boot. The system exists.
To take the images you use a perfectly standard camera. First take the Left shot, then move a suitable distance to the right and take the Right image. Use the same zoom, and try to have the same lighting conditions, aperture stop and exposure time. Center the same point, and donīt rotate the camera (around the axis of the lens). In short, try getting the shots identical, except for the lateral movement. Avoid moving targets, and if you are shooting people ask them to stand still while you get the shots.
If you want to have a natural 3D-look you should move the camera as much sideways as you have between the eyes, that is about 7 cm. To enhance the 3D-effect it is possible to increase the distance considerably however. Once I moved some 20 m (!) to get stereo effect on some mountains several km distant. It worked perfectly, but if you move that much you must ensure that you donīt have any near foreground. Otherwise it will be beyond recognition.
To watch the images in stereo you use the very same technique as for Stereograms, you know the kind of pictures with "hidden" 3D-images within. If you can see such images you use the exact same technique here. There are two ways of doing this: Positively and Negatively. For most people Positive stereo is easier to learn than Negative, and the image seems to get "magnified" somewhat. However, one big disadvantage is that you cannot use pictures wider than the distance between your eyes, some 7 cm (some people say they can manage distances larger than this, myself excluded unfortunately). Negative stereo does not have this limitation, but can be slightly harder to master.
The small pictures in this document are intended to be viewed Positively; this will work as long as they are not displayed too large, which they wonīt be unless the monitor is set to a ridiculously low resolution compared to its size. The following table shows the minimum resolution for monitors of various sizes.
| Monitor | Minimum resolution |
|---|---|
| 14" | 640x480 |
| 15" | 640x480 |
| 17" | 800x600 |
| 19" | 800x600 |
| 21" | 1024x768 |
The larger images, to which you can click yourself, are by necessity placed to be viewed Negatively however.
When you watch stereo images Positively you place the Left image at left, and the Right one at right, next to each other. Then try to look "through" them, focusing the view farther away. You will see "double", but if you succeed two of the images will "fuse together" to form a three-dimensional image.
This may be hard to accomplish for the unpracticed person, but it is like learning to ride a bike, once you have learnt it, it sticks. When the images fuse together at first the view may be blurry, but take it easy and hold the view and it will sharpen eventually. The image seems to "hover behind" the original pictures, and as a consequence of this seems to be somewhat larger as well.
When you watch stereo images Negatively you place the Left image at right, and the Right one at left, next to each other. Then try to look "closer than" them, squint your eyes like when you look at the tip of your nose. You will "see double", but if you succeed two of the images will "fuse together" to form a three-dimensional image.
This way can be even somewhat harder to learn than the former, but it varies from person to person - some think this way is easier. When the images fuse together at first the view may be blurry, but take it easy and hold the view and it will sharpen eventually. The image seems to "hover in front of" the original pictures, and as a consequence of this seems to be somewhat smaller as well.
Meltwater stream on Ålmajalosjekna, July 30, 1996. (138 kB)
Ice canyon on Sarekpaktejekna, August 6, 1998. (58 kB)
Crevasse on Jåkåtjkaskajekna, August 3, 1998. (134 kB)
The icefall of Storsylglaciären, August 2, 1997. (76 kB)
Rundvassbreen's tongue from N, July 29, 2000. (96 kB)
Crevasse on Leirvassbreen, July 29, 2000. (121 kB)
Iceberg from Isvassbreen, July 28, 2000. (68 kB)
Crevasse on Argalaijekna, August 8, 1996. (97 kB)
Flatisen and Flatisvatnet, July 19, 2000. (93 kB)
Fonndalsbreen from N, July 23, 2000. (97 kB)
The steep front of Fonndalsbreen, July 23, 2000. (82 kB)
The heavily crevassed front of Engabreen, July 28, 1997. (93 kB)
The tongue of Engabreen from NW, July 23, 2000. (110 kB)
Ice towers in Engabreen, July 23, 2000. (55 kB)
The ice front of Austerdalsisen, July 18, 2000. (95 kB)
Mørkbekkbreen from N, July 17, 2000. (99 kB)
Crevasse on Austre Okstindbreen, July 26, 1997. (85 kB)
The elegant Melkevollbreen, June 24, 1999. (97 kB)
The crevasses of Briksdalsbreen, June 24, 1999. (114 kB)
Moulin on Briksdalsbreen, June 24, 1999. (124 kB)
Briksdalsbreen crushing forest, June 24, 1999. (141 kB)
Brenndalsbreen from W, June 24, 1999 (139 kB)
Ice blocks beneath the front of Brenndalsbreen, June 24, 1999 (120 kB)
Kjenndalsbreen from N, June 24, 1999 (97 kB)
Fabergstølsbreen in its valley, June 22, 1999 (86 kB)
Nigardsbreen from E, June 22, 1999 (116 kB)
The front of Nigardsbreen, June 22, 1999 (113 kB)
Mountain birch in front of the advancing Nigardsbreen, June 22, 1999 (138 kB)
Fallen down ice block before Nigardsbreen, June 22, 1999 (113 kB)
Bergsetbreen in Krundalen, June 22, 1999 (105 kB)
Ice formation in the front of Bergsetbreen, June 22, 1999 (100 kB)
Austerdalsbreen with Lokebreen, Odinsbreen and Torsbreen, June 23, 1999 (98 kB)
Bingsbreen and Langedalsbreen, June 23, 1999 (89 kB)
Unstable ice bridge on lower Supphellebreen, June 23, 1999 (117 kB)
Bøyabreen and Brevatnet, June 23, 1999 (109 kB)
Rembesdalsskåki and Demmevatnet from N, September 30, 2000 (52 kB)
Crevasses in Rembesdalsskåki, September 30 2000 (103 kB)
The ice cliff of Rembesdalsskåki, September 30, 2000 (70 kB)
Moulin on Ramnabergsbreen, September 30, 2000 (92 kB)
Blåisen from N, September 30, 2000 (79 kB)
Austre Leirbotnskåki from SE, October 1, 2000 (73 kB)
The tongue of Bondhusbreen, June 21, 1999 (84 kB)
The ice front of Øvre Buarbreen, June 20, 1999 (88 kB)
The ice front of Nedre Buarbreen, June 20, 1999 (120 kB)
|
Top of document |
Stereo images |
Site map |
Email the author |
Copyleft information |
Detta dokument på svenska |
| Last updated: March 17, 2001 | Unless otherwise specified; text, tables, photographs, maps and other graphics © 1999-2001 Gunnar Ljungstrand | |||||