Viewing stereoscopic pairs

Links to commercial web sites are for information only and do not mean their products or services are recommended. 
Nobody paid to get mentioned here, but some have emailed further information, which is always welcome.

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How to see 3d Pictures

Three dimensional photographs require two pictures of the same scene from slightly separate viewpoints. Some mechanism is needed to present the right shifted picture to the right eye and the left to the left eye.

On this site, free viewing methods are advocated, needing no special equipment.  It is important for chemists to learn cross-eye free stereo viewing as X-ray crytallography is often presented in scientific journals in this format.

The X picture format used on this web site is compatible with most methods depending on optical aids, by using readily available, free conversion programs.

This web site was started in 1995 and small computer screens were used then. I currently (2008) use a large, 22 inch, LCD screen, which is less than half the price of my original VGA monitor. Most images on this web site are currently small, for an 800 pixel wide browser window. It is just as well the pictures still have small file sizes, because New Zealand Telecom has failed to keep up with modern broad-band requirements, even where I live in Auckland, the largest city. Some larger versions are starting to show up on Flickr. Large 3D images benefit from optical viewing aids.

Optical Stereoscopic Viewers

No attempt is made to describe the many available viewers as  commercial stereoscopy web sites are so helpful. For neophytes contemplating an optical viewer, systems used by the author are reviewed, which might clarify the choice.

{3dstereo  Berezin: a large variety of slide and card viewers}, 
{Amateur Instruments} Some are very good, a few are for sale.
{Ralph's 3d viewer page}
{Professional stereoscopes}  { Photogrammetry }

Commercial viewers are available for U stereo and split image X stereo. They give a more restful stereoscopic experience than free viewing.

X stereo (cross-eye stereo)

is the preferred format for free viewing, as it allows fusion of large stereo pairs without any external aid, which is why it is the basic system on this web site.

{Loreo viewer} works on split image 4 by 6 inch prints. The Loreo "lens in a cap" produces U stereo images directly and there is a suitable viewer provided, except that it is not useable by old people with presbyopia.
{Vivitar viewer} does (is) the same and these prints are in cross eye format (X). This can also be used for viewing computer 3D in X format, Since it uses mildly magnifying lenses, use your distance prescription, but not reading glasses.

U stereo  (Parallel eye stereo)

Optical viewers for full resolution computer parallel (U) stereo must diverge your vision to fuse the large images.

• Most people anticipate objects in a viewer will be close at hand and their eyes converge automatically. 
• The viewers are usually set up for infinity viewing, which requires the eyes to have maximum divergence, to parallel.
• Any viewer is not going to fuse images for neophytes at first and better versions start converged, then slowly diverge under user control once fusion has occurred. Computer software may allow this change since most computer viewers do not. ScreenScope has the best convergence adjustment and is strongly recommended, but it is expensive.

 Slide viewers and hobby glasses are pretty useless on a big computer screen.
Magnifying viewers with prism lenses (Holmes type) make the monitor pixels spring into view, so they have  limited value.

Over/Under stereo, OU, KMQ

This format is for postcard size prints, where the Right eye print is positioned over the Left eye print. This is very useful for prints as they return from the lab and placed in a photo album, ideal for those starting in 3D photography. They are seen in 3D using  a View Magic 4 mirror viewer or KMQ prism glasses.

example

Stereoscopic viewers for  a computer include:

• Four mirror Cazes viewers (modified Wheatstone principle).
  • side by side
    • Tyrell mirror viewer (jpsVisor) (Poland, shows up on eBay at times)
    • ScreenScope (Australia, but cannot be purchased from the NZ agent because of a ridiculous mark-up. Get a much better deal from Berezin)
• over and under
  • View Magic (USA) (See KMQ for a prism alternative).
• back to back
  
  
• Pairs of small angle prisms
  • NVPD (Switzerland) U stereo
    Pokescope (USA) U stereo
  • KMQ (USA): Over and under pairs.
    
    
• Pairs of prism lenses (Holmes type viewers, small U images if the stick is removed)
  • Lorgnette (Made for prints but work on small U stereo computer images)
    
    
• Anaglyph coloured glasses (not too good for colour stereo but fine for monochrome)
• {Liquid Crystal Shutter Glasses}
  ( The link given here compares the many different versions available. Shutter glasses work with CRT and Plasma displays but not slower changing LCD screens.)
• { Polarising viewers }
  • Polarised 3D is common in movie theatres using two simultaneous projectors, but has only very recently become possible on computer monitors.
    • (RealD) Uses a single projector with rapidly alternating R and Left frames and alternating polarised filters so that simple circular polarised filters can be used by the audience. Circular rather linear polarisation allows some head tilting)
  • An attachment over the computer screen provides polarised 3D, which is viewed through  cross polarised "sun glasses". Operators can see the real world, without flicker, simultaneously with 3D monitor images. This is vital during stereoscopic endoscopic surgery, for example. 

• Lenticular prism screens Allows computer stereo without optical aid and without going cross-eyed, but the single oberserver's seating position is critical.

• Pulfrich principle for moving images

• Other ideo-syncratic systems.

  • [ mirror stereo.]

    • Holoblade (Japan, over/under mirror images)

  • [ chromastereopsis ]

  • Stereoscopic projection systems run by a PC are an alternative viewing system, but not described here because simple computer monitor viewing is being advocated. (See here as an example)

Prism Viewers

Instead of using four mirrors, two base out prisms are used to diverge vision onto wide stereo pairs.

Loreo make a cheap version out of cardboard suitable for mailing with stereo cards.

PokeScope. 
You do not need PokeScope software to use this small, pocket viewer.

*  Pokescope has two, approximately 7° deviation prisms, which diverge vision onto those stereo pairs which are too large for free U viewing.
*  Distance from the stereo pair is variable since there is no lens.
*  A built-in window acts better than the septum in a Holmes viewer, so each eye sees only one of the paired images, when the Pokescope is at the correct distance for optimal viewing.
*  The window shape is perfect for computer full screen stereo pairs.
*  The stereo windows can be adjusted slightly, independent of the prisms. Change in optical divergence is almost zero as the prisms rotate. (Unlike adjustable 4 mirror viewers, where light divergence is more extensively variable when one of the mirrors in each channel is turned. But if you rotate the whole mirror assembly for one channel, the divergence does not change, much like Pokescope's prisms).
*  Pokescope folds neatly to pocket size, protecting the glass prisms.
*  It works on large aerial photographs or stereo X-rays (but not as good as a  4 mirror viewer).
*  Works very well with reading glasses. 
*  For stereo cards, wear hobby glasses while using a Pokescope to get magnification, since the prisms are not positive lenses.
*  Keep accessory glasses and the Pokescope in a pocket: this warms them up and stops the lenses fogging.

-  Pokescopes will not handle "over and under" format.
-  Horizontal (landscape format) post-card pairs are not ideal for any but the over/under viewer and the 3:2 window Pokescope has limitations compared with free X viewing. It works nicely for vertical postcards, with a little panning, but shows horizontal postcard pairs at smaller size, since you have to look from further away.
*  More advice on using a Pokescope [here.]

See also NVPD prisms, which I personally find easier to use.

Holmes Viewers

The classical viewer that popularised stereo cards uses two prism magnifying lenses in its best form. 

• Often normal magnifying lenses are used, with optical centres 3 inches apart (76mm). This means normal people  look through the lenses off center. That turns them into base out prisms whose divergence increases as the inter-ocular distance decreases, meaning they work for children and adults without needing an inter-ocular adjustment.
• The sliding bar is not only for focussing, but also for divergence control. Most people cannot relax their eyes when looking at something nearby and initially fail to fuse the images.
• The best procedure is to place the stereo card too far away at first, where it is probably out of focus, as this reduces the divergence needed to fuse the images. Once they are fused, slowly slide the card closer until it is in focus. Simultaneously the observer's eyes painlessly diverge, until the picture is seen in sharp 3D.
• Most Holmes stereoscopes have the lenses set too close to the focus bar. Portrait format pairs (4 or 5 by 3 inch) are better seen with the lenses elevated a bit and the common 3x3 inch square pictures are still seen well.
• Holmes viewers can still be purchased.
  A superior version is made by {Lewis}. It uses achromatic lenses set higher than "normal", which are both improvements - at a price. Higher lens position is needed for portrait format 3D pairs, which fit a standard post-card nicely. Traditional Holmes format is virtually square and the traditional viewers are not so good for portrait format.
• Ancient viewers are pictured {here}
• Keystone viewers { here }

Plastic prism lenses.

It is not necessary to use a Holmes viewer. Excellent results are achieved with plastic lorgnette viewers, described on the commercial web sites.  These are cheap enough to include with a set of Holmes cards for posting to friends. 

• The "Added Dimension" unit has a longer focal length than some Holmes viewers and is capable of showing vertical format 4x6 prints even better than a Pokescope - and a lot cheaper too.
• The smaller U stereo pairs on this web site work with a lorgnette viewer, at the expense of seeing pixels too well. The Pokescope is much better, as it works nicely on the bigger, higher resolution U pairs.
• A Holmes viewer has the advantage that each eye sees its own picture (near enough, because of the short septum). Some Holmes viewers have a removable bar, letting them work on 3d books and computer screens.

Stereo Binocular

The best card viewer with achromatic lenses and a built-in light  comes from Keystone (who used to make commercial stereo cards until about 1939). It is actually  for opticians or ophthalmologists interested in  diagnosing and treating binocular visual defects, but it has superb optics and controls. It would cost, posted and packed, nearly $NZ2000.00 !  However much cheaper versions come up on e-Bay

View Magic mirror stereoscope and KMQ prism glasses

Used for postcard size 3D pairs as prints, just as they come from the processing laboratory, placed right eye above left eye, often in a postcard album.

Brewster Viewers

An excellent description of a home-made slide viewer for medium format transparencies, constructed from custom wood on a Triton work bench, comes from Australia. It is not essential to use the expensive lenses described.
{ Here }

High quality commercial slide viewers, made of metal, in Holland:
{ DeWijs }.

Anaglyph glasses

See the [ anaglyph section ].