Mirror or Prism assisted viewing
Large stereoscopic image pairs on a computer screen can be seen by cross-eyed viewing. (X stereo). Beginners find cross eyes produces a headache, so an easier method has been devised.
Mirror assisted viewing (m stereo) requires one of the pictures to be flipped over. It returns to normal orientation when seen in a mirror. The normal image is looked at directly with one eye. The mirror is adjusted over the other eye until the two pictures superimpose.
This is far simpler than methods often described on the Internet such as
liquid crystal shutters and flickering images. It will even work for moving pictures.
Russian method for books
View with screen minimum 800 pixels wide.
|Right eye Image||Left Eye Image|
|U stereo version (parallel eyes) Pan to the right and use the middle two pictures.|
|The middle two pictures from this set of four can be used for U stereo: parallel eyes. Move away from the screen if the separation is too great or use a 4 mirror viewing system (Cazes viewer).|
Go to Start
Hyperstereoscopy means the two photographs have been taken with a separation greater than the distance between human eyes. Normally we cannot see in 3D beyond about 200 meters. By making our heads as big as a WWII battle-ship range-finder, we could see distant objects in 3D. As that is impossible (without genetic engineering), it is easier to use hyper-stereoscopy for this delightful effect.
This hyper stereo pair, showing Lake Hayes, was photographed by John Wattie.
It is a "running stereo". A suitable site on the river terrace
at the foot of the Crown Range was chosen. The left picture was taken first,
then the photographer ran very fast and took another. The result is: the viewer
seems to have a head as big as a small hill. The model effect then takes over,
since we do not think of ourselves as giants. The brain assumes this is a small
model of reality.
(Hyperstereoscopy without model effect is discussed here: PePax)
It was a fine Central Otago day - no clouds to move in the sky and spoil the stereo. The original transparencies show some sheep moved between the two exposures, but the version here has such low resolution you cannot tell the little white dots in the nearby fields are not quite right.
This valley is famous for its geomorphology, showing the effects of ice-age glacier carving. For a discussion of glaciers, press [here].
The more common version of prism viewing is using shallow angle prisms over each eye, thin edge in. These bend the light sideways. U format stereoscopic pairs too big for parallel stereo can be fused.
The [Pokescope viewer] uses shallow prisms deviating light about 7° and is good for parallel computer stereo, as on this page (U stereo).
Close viewing of the computer monitor with a Pokescope causes keystone distortion, where the center part of the pair are magnified more than the lateral parts. This differential, vertical magnification spoils the stereo effect in the same way camera convergence during stereo photography causes keystone distortion. The pictures become hard to fuse. So you need to sit back in the normal place and not lean towards the screen while using diverging prism viewers.
The up side is: pictures taken with camera convergence have distortion in the opposite way, bigger laterally. So excessive divergence with a Pokescope potentially corrects keystone distortion caused by macro photography with convergence. (See [how to take stereo pictures] for more on keystone distortion).
Mirror stereo on a single flat screen also suffers from distortion, which is why John Hart's rig - mentioned above - uses pictures horizontally angled relative to each other. Mirror stereo on two computer monitors can also be corrected for distortion by angling the screens.
3D contents page
Stereo Picture Gallery
Escape from 3D: New Zealand Images
Back to the home page