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Stereoscopic Cave Photography

              Photographing in the dark by painting with light

John Wattie

 

 

Contents:

  1. Painting with Light in caves
  2. Hyperstereoscopy
  3. Tricks for enhancing the 3D effect in caves.

Images:

Painting with light

Komrad is a "wild cave", not a commercial cave. It is not easily found unless you join a speleological society trip. It is near Waitomo, in New Zealand. Illumination is not electric lights, as there is no power in this remote place.
Lighting is just one electronic flash gun.
Two cameras were set up side by side on tripods, the shutters were opened and then the photographer wandered about in the dark cave firing the flash from predetermined sites.
This is slightly dangerous.
Gradually, over about 20 minutes, the picture was built up on the two film frames.
This is "painting with light". Light painting cannot be duplicated exactly, so 3D photography with just one camera and two exposures does not work well.

Hyperstereoscopy

The two-camera method has introduced slight errors. The colour balance is not the same (since the films were different batches and the 50mm lenses were not identical - one was an Exacta and the other a Nikon.) This has not quite been corrected in PhotoShop. The cameras were not quite on the same horizontal line, but that does not cause much trouble - the human brain is amazingly tolerant of small errors. The 3D is enhanced because the cameras were further apart than human eyes. This is called hyperstereoscopy.

A strange illusion shows up in hyperstereoscopy, called the model effect. Because the viewer seems to have eyes much further apart than normal, it is as if he/she were a giant. We do not think of ourselves as giants and get an impression the 3D objects are smaller than normal. Since you have no idea how big this cave was, the fact it looks only about 1/2 normal size is no problem.

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stereo2.jpg (74042 bytes)

Taumatamaire  Cave Passage  in X Stereo        Taumatamaire Cave Passage in X Stereo

Right Left 

stereo2.jpg (74042 bytes)stereo2.jpg (74042 bytes)
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Taumatamaire                   Taumatamaire 

in U Stereo                     in U Stereo

Right Left Right Left

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Taumatamaire cave passage in anaglyph format.

This requires red / blue-green glasses: Left eye red, Right eye blue-green.

 

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Methods for enhancing stereoscopy in caves

  1. Looking down a passageway, since the perspective of the walls getting smaller reinforces the stereoscopic information.
  2. Reflections in a pool or mirror are included, since the reflections are behind the surface.
  3. Under an overhang or roof. A ceiling or tree branch strongly enhances stereo, because objects gradually and imperceptibly merging into the distance are suddenly contrasted with a near-by overhang. The sky does not provide this effect.

Further mystery is seen in the Taumatamaire picture because the text "X Stereo" and the photographer's name seem to lie inside the rocks.
This stereoscopic illusion only works with black rocks. Rocks whose surface is lit by the flashgun become very confused if something is inside them. The brain will not accept it, since this is contrary to normal experience (unless you are Superman, with Xray vision of course).

Komrad Cave in X Stereo                                      Komrad Cave in X Stereo

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g

Komrad Cave  in U Stereo                Komrad Cave in U Stereo

Right Left Right Left

  Use the two middle pictures. (Pan right first, if you have to).

  If the separation is too great for your eyes, move back from the screen.

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Go Up "Painting with light" is dangerous, since the photographer has to wander about in the dark firing his flash and could easily fall down a hole.
Intermittent light from a torch is used, but great care is needed not to shine any light towards the cameras.
Sometimes dim candles are lit behind rocks and since the exposure times are very long, (30 minutes or more for this one) the candle begins to illuminate the picture. This is often set up on purpose, since the distant red glow of flame adds to the cave's mystery.
Another trick, used here, is to keep light off the near-by cave. This adds to the sensation of darkness since we seem to be looking out of a dark passage into an illuminated chamber, as indeed we are.

It is easy to use too much light in cave photography and rob the cave of its essence - stygian darkness.
It is also easy to use too little light. Light seems to be absorbed in a cave, since the chambers are usually so big that reflection off the walls is minimal. The guide number for flash guns is quoted for indoor photography and is optimistic for outdoors, or big caves.

The cave images featured here were obtained with the help of John Pybus, Prof. Robert Boas & Prof Gary Barnes.

 

 3D contents page

Stereo Picture Gallery

Escape from 3D:  New Zealand Images   

    Back to the home page          

 

More macro stereo and cave stereo photography (from Australia) 
at David Stuckey's Site:
http://www.acay.com.au/~dstuckey/framesetf.html