A Guide for New Stereo Photographers

By the "Victorian 3D Society"

Introduction

This guide is intended to help orient new Club members to the world of stereo photography by covering many of the areas that new members often ask questions about. In such a short guide I can only introduce you quickly to the most important technical aspects of stereo. Other less technical subjects, such as where to source stereo equipment, and what other Stereo activities and organisations exist, are also presented.

The Victorian 3D Society

The Victorian 3D Society is a special interest group for active stereo photographers. I stress here that we actively take stereo photographs ­ I like to think that none of us is an equipment collector! We hold six General Meetings each year (on the first Monday in every "even" month), and six Committee Meetings (on the third Tuesday in every "odd" month). Anyone is most welcome to attend any of these meetings. General Meetings are held at the "Horrie Watson Pavilion" in the Deepdeene Park, off Whitehorse Road, Balwyn (Melway Map Ref 46 A7), located in Melbourne, Australia.

Stereo Photography

Stereo photography is perhaps more widely recognised by the general population as "3-D" due to their exposure to such movies over the years. Many are also familiar with the "Viewmaster" reels that are popular with children. Stereo photography is even older than either of these - Charles Wheatstone was actually drawing stereo images in 1832 before photography was invented!

The reason that people have stereoscopic vision is because we have two eyes. The eyes are on average about 65mm apart, and so they see a slightly different image of the same scene. Objects that are close are seen to block out different parts of other objects behind the close object when we alternate the view between each eye. This is called parallax. Stereo photography relies on reproducing this parallax by taking two photos of the same scene (perhaps with two cameras) spaced apart (most often by about 65mm). To see the photo stereoscopically, the left eye must view the image taken by the left camera, and the right eye must view the right image. Special mounts for mounting the images are required, together with a stereo viewer with a lens for each eye. Stereo images can also be projected, or printed, but still usually require some form of viewing aid (such as polariser, or coloured glasses). Most Club members take stereos using colour transparency film on 35mm format.

Equipment Required

People new to stereo are naturally concerned about what equipment they need, and where to get it ­ this concern never really goes away incidentally! In my opinion, the minimum equipment requirement for any stereo photographer is as follows:

 

The equipment above is designed for use with slide film. Kodachrome 64 or Kodachrome 25 are most suited for use in stereo due to the very fine grain structure of these films. Fuji Velvia or Fuji Sensia are also excellent. Grain is far more evident in stereo than in mono.

Stereo Cameras

As it has been many years now since useful stereo cameras have been made commercially, only second hand units are available. If you are starting out in stereo, I would recommend that you obtain one of the many stereo cameras that were made during the 1950's, when stereo was in its last heyday. Generally, the quickest way to find one is to write to the second hand equipment outlets listed later. Only occasionally do stereo cameras appear for sale in some Melbourne camera stores (eg: "The Camera Exchange"), usually at very high prices. Below is a list of some appropriate stereo cameras (all are "Realist Format" unless noted otherwise):

 

While these cameras are now getting very old, they will teach you a lot about stereo ­ particularly in relation to the "stereo window" (see below). It is important to get such fundamental issues "under your belt" before using other techniques for taking stereo pictures. Using one of these older cameras is the recommended starting point for beginners.

Currently Manufactured Stereo Cameras

 

Light Meter

If you are using one of the many stereo cameras in made in the 1950's, then you will definitely need a light meter. The Edixa Model III is the only one that had a built in light meter ­ but I would not trust the accuracy of it except in an emergency.

Light meters can be bought new, or second hand. Many club members use the classic Weston Master series which can be bought for about A$60 second hand. If buying a light meter second hand it is wise to check its accuracy against another light meter that is known to function correctly.

Film Cutter

Film cutters can be bought new from most photographic stores. The "HAMA" range of photo- accessories includes several types of cutters of varying complexity and price. The best film cutter I have seen was made by the Stereo Realist company - it has two adjustable prongs to ensure that each image cut is exactly an integral number of sprockets wide. This is a handy feature, particularly with the "Realist" format where the width of the film chip to be placed in the mount is normally only marginally wider than the mount's aperture.

Stereo Slide Mounts and Tape

Stereo slide mounts are normally best bought through the Victorian 3D Society. Keith Hutchings holds the current Club stocks, which are sold for $10.00 per 100 mounts. The table below lists the sizes that are normally available.

 

Aluminium slide mount masks are available from Reel 3D Enterprises in the United States. The cardboard covers listed in the table can be used in conjunction with Emde Realist format aluminium masks to produce a very high quality mount.

When using the Club's cardboard mounts, the film chip is best held in position using tape. The best type of tape is Scotch #850, as the adhesive used will not "bleed" like normal sticky tape does after a period of years. This tape, along with a variety of other cheaper tapes that are also non-bleeding is available from: C P Supplies, 114-118 Campbell Street, Collingwood, Australia, Phone: +61 3 9417 4191.

Slide Mounting Jig

A slide mounting jig is used to hold the mount, and two film chips while you precisely adjust the position of the film chips for correct mounting (see below also ­ Taking Stereo Pictures). The designs of some mounting jigs are given in Reference 1.

A mounting jig is also available from kiewa Valley stereo.

Stereo Hand Viewer

A stereo hand viewer is required to view the slides. It is possible to project your slides with a projector too ­- usually with home built or modified units. This is something to think about much later. Once again, Reel 3D Enterprises in California can supply new battery powered viewers, with focussing adjustment for around US$50 (Late 1992).

Second hand viewers are actually harder to get than second hand cameras ­ although it can be worth trying as you may notice an improved image because many of the older viewers had "doublet" lenses.

Taking Stereo Pictures

When taking a stereo picture, it is advantageous to ensure that the scene actually has depth in it! For example ­ a stereo photo of a valley taken with the camera right at the edge of a cliff will result in little stereo effect in the final stereogram. This is because under such conditions most of the subject would be over a few hundred meters away. At these distances, and with our 65mm separation of our eyes (and camera lenses with a conventional stereo camera) little or no parallax error will result between left and right images. When the parallax between left and right images is small or zero, the scene looks mainly "flat" or without depth ­ both in real life and in a stereogram.

Instead it is best to include foreground and middleground objects to provide a continuum of depth in the scene. Obviously this may not always be possible. In the above example the solutions may include: move back from the cliff edge to include foreground objects (provided they are still in context with the scene ­ ie: no parking meters etc.); move to include parts of the cliff formation in the middle distance; or use an increased separation between camera lenses to artificially increase the parallax between left and right images. This last technique is called a "hyper- stereo" as the resulting stereo effect is exaggerated. It is an advanced technique and will not be covered here (see Ref 1 for more information).

There is a limit to the amount of depth that should be included in any stereo scene. This limit results from design decisions made regarding viewing and projecting devices. The reasons for these design decisions are best covered in Reference 1. In practical terms however, the conventional stereo camera with 35mm focal length lenses separated by about 70mm, is designed to handle a depth range from 2 meters (7 feet) to infinity. Photographs taken that only include objects in this depth range will view perfectly well in any viewing device (once properly mounted). If objects closer than 2 meters must be included in the scene, then objects at or close to infinity must be excluded. Reference 2 recommends the use of the following depth ranges when using a "Realist" format camera:

 

In accordance with the above depth ranges, there are three types of stereo mounts for the "Realist" format ­ normal, medium, and close-up. (The "Realist" format is by far the most common used by conventional stereo cameras. The depth restrictions exist for other formats too, but will not be covered here.) When taking and mounting stereo photos with a Realist format stereo camera these depth limits must be observed if comfortable viewing is to be achieved.

The Stereo Window and Mounting Technique

This is far and away the hardest aspect of stereo photography to understand and explain. Fortunately for users of the Stereo Realist system it is possible to successfully take stereo photos with just a little knowledge of the stereo window as most of the important parameters were automatically designed into the system. Other formats require a better knowledge of the stereo window.

With a stereo photo, everything assumes a position in space. It must ­ this is the aim of taking stereo photos. However, it often takes a little while for the beginner to realise that the frame around the edge of the picture (formed by the two apertures in the stereo mount) also assumes a position in space. It is the depth position of this frame relative to the depth position of the images in the photo that is important to understand. The frame formed by the apertures in the stereo mount is said to create a "window". A good rule to keep in mind when mounting a stereogram is:

When mounting a stereo photo the aim is to make the image appear as if it were being seen through a real window.

This statement does not appear to say very much. The importance of this concept is however often under-estimated. To achieve the above goal when stereo mounting, the vertical and horizontal positioning of each (left and right) film chip must be strictly controlled.

Vertical Positioning

Take a look now through a real window. First with your left eye, and then with your right, making sure your head is vertical. Concentrate on one particular object that is beyond the window, but partially obscured by the frame at the bottom so you only see part of the object. It will be seen that the frame of the window cuts through the same point of the object in both your left and right eyes (provided of course that your head is vertical as normal!).

Keeping in mind the rule above, this means when mounting your stereo pair, that the bottom edge of the mount's aperture must cut through an object in the left image at the same height as in the right image so you see equal amounts of the object in each image.

Under ideal conditions this means that the film chips are level with each other. Some cameras however introduce small vertical errors due to manufacturing tolerances on lens positioning, and often the cardboard mounts have a vertical error in the position of the left and right apertures. This means that it is always best to adjust vertical position of each film chip to meet the above criterion. In general, the maximum vertical error should be less than 0.1mm.

An example of vertical positioning error in mounting - the right hand film chip is too low relative to the left hand film chip.


Horizontal Positioning

This is where many come unstuck. It is the horizontal positioning of the film chips that determines the position in depth of the image relative to the position of the window. You should remember now that the window for any mount is fixed in space nominally at 2 meters (7 feet) distance, and that moving the film chips apart makes the image further away, while moving the chips closer together makes the image closer. How can this be used then to satisfy the mounting rule above? Take another look out your handy window. Once again alternate your view with your left and right eyes ­ but concentrate on objects near the left edge of the window.

Distant objects (at "infinity") near the left edge will only be visible with your right eye. However, if you had an object immediately behind the window -- touching the glass -- then both eyes see an equal amount of the object! For objects between the window and infinity, more of these become visible in your right eye with increasing distance. (Similarly, your left eye sees more objects at the extreme right than your right eye.) To mount your stereo pair correctly you must ensure that the above condition is duplicated.

There should be no instances of the left eye seeing something on the extreme left that the right eye can't see. (And no instances of the right eye seeing something on the extreme right that the left can't see.) Such a condition is referred to as being "in front of the window" and is considered incorrect mounting because such images do not occur in reality.

An example of incorrect horizontal positioning in mounting. The closest objects are "in front" of the window because the film chips are too close together, causing d2 to become less than the aperture separation d1.


An example of correct horizontal and vertical positioning in mounting ­ the closest objects are just behind the window.


Any twist or rotation of either image can ruin an otherwise correctly mounted stereo pair.


Depth of Field

The use of "depth of field" in stereo photography is different from it's use in planar photography. Low f-numbers are often used in planar photography to deliberately de-focus certain zones in a photo. A classic example is a portrait with an out-of-focus background. It is generally recognised that this should not be done in stereo. I believe that the very real-looking images that result from stereo cause confusion if the eyes cannot focus any part of the scene (as they can in reality). The aim in stereo is to maximize the depth of field (consistent with practical exposure times). Setting the camera's focus equal to the hyperfocal distance is helpful here (see Reference 1).

Stereo Formats

Stereo Realist

The "Realist" format is also referred to as the "five sprocket" format as each image (left and right) occupies five perforations along the length of the 35mm wide film. The image size produced by the camera is 23.5mm wide and 24.5mm high. The stereo mount into which each image is mounted is 41mm high and 101mm wide.

European Format

The "European" format is also referred to as the "seven sprocket" format as each image occupies seven perforations along on the 35mm wide film. This gives an image width of about 32mm, however the standard mount has apertures 28mm wide. This gives enough latitude to move the films chips further apart so that close subjects can be mounted correctly. The stereo mount has the same external dimensions as the Realist format. (Note: Standard SLR 35mm cameras produce an image width occupying eight film perforations.)

2 x 50 x 50

This format uses two standard 50mm x 50mm mono (2D) slide mounts to mount the left and right image. It is also known as 2 x 2" x 2". This format has become more popular (particularly for projection) in recent years, perhaps due to the lack of modern stereo equipment. Left images can be held in the slide cartridge for one projector, and right images in another. Cameras for this format are usually twin SLRs mounted on a bar. The format is difficult to use for hand viewing, although frames are available for holding two standard mounts side by side for appropriate viewers.

Viewmaster

Invented by Wilhelm Gruber in 1938, this format uses reels that contain seven exposed stereo pairs with images of 11.7mm wide and 10.5mm high. Up to 69 pairs of images could be shot on 35mm film using Viewmaster cameras from the 1950's. Popular still today are the commercially produced reels with photos on virtually any subject.

Nimslo

The Nimslo camera was released in the early 1980's and was designed to make stereo prints. The camera has four identical lenses, each producing an image 18mm wide and 22mm high. The system (which worked as intended) was basically a flop, and cameras were eventually sold at greatly reduced prices. Many enthusiasts have modified Nimslo cameras for a variety of uses. Stereo Cards

The stereo cards that were very popular at the turn of the last century are designed to be viewed with a "Holmes" viewer. Both the left and right prints are mounted on a card 180mm wide and 90mm high. Each print is usually 90mm square. Some Club members collect these old stereo cards. It is possible to use a Realist format camera with print film to make your own stereo cards.

Other Techniques

While I recommend that you obtain a standard stereo camera, there are other techniques for taking stereo photos. If you have a normal 2D (mono) camera you can use it to experiment with stereo by taking the left photo first, then moving the camera an appropriate amount (see below) to the right and taking the right photo. It is imperative that the scene is static (does not change between exposures), and important to keep the camera level, and always pointing in the same direction (do not rotate or toe-in the camera) between exposures. Naturally indoor scenes or "table-top" photos suit this technique. As a guide only, the distance you move the camera between exposures should be 1/25th the distance to the closest object in the scene.

If you have two SLRs or similar cameras you could also mount these on a bar to make your own stereo rig. Naturally you will need to devise a way to release the shutters simultaneously (eg: cable, solenoid or electronic). Shutter synchronisation needs to be better than 1/500th of a second for action photography. Such a set up also allows you to vary the focal length of the lens, and base separation between cameras. The effects of such changes are worth investigating eventually and are discussed well in Reference 1.

Another alternative for SLRs is to use the so called "beam-splitter" which attaches to the front of the existing lens. It uses mirrors (or prisms in more expensive models) to combine a left and right view into a vertical format stereo pair on the film. The system is designed for use with lenses near 50mm focal length. A small amount of trapezium (or keystone) distortion is introduced by these attachments. This, together with the vertical format has probably limited their popularity.

Stereo Organisations

Australian Stereo Organisations

 

* Sydney Stereo Camera Club. A very active Club with an informative Newsletter published six times yearly. Meets once per month. Contact: Allan Griffin, Phone +61 2 9488 8798.

* Victorian 3D Society. General meetings six times per year. Stocks stereo mounts, publishes a Newsletter, and has a slide folio circuit. Single membership $10.00 per year. Contact: Max Hem, +61 3 5787 1088.

* Stereoscopic Society ­ Australian Division. Circulates Australian, Australian and New Zealand, and Overseas slide folios. Has a literature library. Contact: Terry Kane, Ph: +61 3 9870 2714.

These three organisations also participate in the Australian National Stereo Convention, which is held once every two years.

International Stereo Organisations
Not all adresses have been updated at Jan 1997

 

* International Stereoscopic Union (ISU), c/o Judy Fentress, PO Box 19-119, Hamilton, New Zealand. Publishers of "Stereoscopy" magazine. Individual and Club membership supported. Holds a Convention once every two years.

* National Stereoscopic Association, PO Box 15801, Columbus OH 43214, USA. Publishers of "Stereo World", a bi-monthly magazine devoted to old and new stereo photography. Stereo Equipment Sources

* Reel 3D Enterprises, PO Box 2386, Culver City, California 90231, USA, IDD-Phone: 0011 1 213 837 2368. Publishes a new equipment catalog. Sells new mounts, books polarised glasses, viewers etc Publishes used equipment listings VISA/MASTER card, phone orders.

* David Yong, 7-12-3 Taman Seri Damai, Lebuhraya Bat u Lancang, 11600 Penang, Malaysia. Supplies Realist format and 7 sprocket format mounts.

* Stereo Photography Unlimited, 1005 Barkwood Ct, Safety Harbour, 34695-4401 Florida, USA, IDD-Phone: 0011 1 813 726 3356. Prices usually higher, but has large selection of used cameras. 90 Day Guarantee. VISA/MASTER card phone orders.

* Mr Harry Poster, PO Box 1883 So. Hack, NJ 07606, USA. IDD-Ph: 0011 1 201 794 9606 or 6696. Used cameras and viewers of all brands. No credit card facilities.

* Ron Speicher, Box X, Far Rockaway, NY 11691, USA. IDD-Ph: 0011 1 516 868 6411. Used cameras, viewers, projectors. Payment with Bank Cheque.

* Dave A. Berenson, 32 Collwell Avenue, Brighton, MA 02135, USA. IDD-Ph: 0011 1 617 254 1565. Used cameras, viewers, projectors. Payment with Bank Cheque.

* Ron Zakowski, R.R.2, Box 638, Wautoma, WI 54982, USA IDD-Ph:0011 1 414 361 2524 (Number not confirmed). Ex-"Realist" employee, and provides parts and service for the repair of Realist equipment. Stereo equipment bought and sold.

* Dalia Miller, PO Box 492, Corte Madera, CA 94925, USA. Has an excellent catalogue, with nearly any make/model listed.

* Pop-Optix Labs, 241 Crescent St, Waltham, MASS 02135, USA. Leep Stereo Camera & Viewer.

* 3-D Source, Box 14306 Austin, TX 78761, USA. Viewmaster equipment and mounts.

* F W Trembley, Box 310, Hialeah, FL 33011, USA. Conversion kits for viewing Realist or larger slides with Viewmaster.

Further addresses are also given in Reference 1.

References

1. Ferwerda, Jac G -- "The World Of 3-D" Second Edition, 3D Book Productions, 1987. Highly recommended and currently available -- a must for any Stereo photographer.

2. Morgan, W D and Lester, H M -- "Stereo Realist Manual" New York 1954. The classic text on the Stereo Realist system.

3. Gowland, Peter -- "The Art and Technique of Stereo Photography", Crown Publishers, New York, 1954. A less technical book long out of print, but sometimes available through some of the listed dealers.

Victorian 3D Society
Thursday, November 25, 1993
Updated January 1997

 


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