Dukes Stereo Opticard - Possibly the best stereoscope you will ever own

In the pantheon of stereoscopic viewers, I think this one deserves a special mention. This is a stereoscope that was created by John Dukes.

John writes (in the instructions): “This viewer grew out of my frustration with the disparity between what seemed to be magnificent photographs on some of my old viewcards, and the dismal system I had for viewing them. Having fought the battle to bring “ortho” viewing to View-Master slides, I wondered if it might be possible to view cards awe well.”

He continues: “Every cards I looked at seemed to be improved with lenses shorter than the roughly 200mm focal length system in most Holmes slide viewers. So I used 100mm (focal length) lenses and was astonished at the impact. And several of my cards seem to be so life-like that I wondered if maybe they were in fact photographed with 100mm lenses! But ALL of the cards were much more fun to view. I hope you will agree.”

John build his first Opticard around 2002. These were sold directly to stereo enthusiast by John and also through Jon Golden of 3D Concepts.  I do not know how many viewers were made, probably around 50-100 (John told me around 50). They rarely show up for sale. In a photo-3d posting, Jon Golden mentioned that the last run of 20 viewers was ready for the 2004 NSA Convention.

What is so special about this stereoscope is that it does not use prismatic lenses. Now, prismatic lenses are required when you have stereoscopic images that are wider than the spacing of the eyes. John solved this problem by using achromatic lenses of very large diameter and short focal length. The large diameter takes care of the mismatch between eye separation and stereo pair separation. The short focal length produces large magnification to see all the details in the image. That's the summary.

Here are the specifications of the Dukes Opticard, from a posting from Jon Golden in photo-3d: The OPTICARD has high quality 50mm diameter, 100 mm focal length coated achromats. The optical stage has a 1.5cm interocular adjustment range, to accommodate even poorly mounted vintage view cards. A twin lead-screw mechanism, provides moderate individual focusing for each eye, and covers approximately + or - 1.5 diopters overall. A very bright, cool-running, built-in fluorescent diffuse light source, is carefully positioned to avoid distracting shiny reflections on the stereo viewcard surface. Estimated bulb lifetime: 6000 hours. Front-panel On/Off light switch. Machined aluminum components are anodized black, with a solid walnut front panel. 120V AC w/cord and two prong plug, Weight: 7lbs, Dimensions w/ handles: 12in. width x 10 in. height x 6in. depth.

And here is my personal experience (recorded through an ebay sales description – sorry if some points are repeated):

I bought this stereoscope around 2004. I know John Dukes personally and I admire his ingenuity and stereo skills. He has produced other amazing products too.  I used the viewer for a couple of days, and then put it away.  I did not touch it until a couple of years ago. I am not a big stereoview collector and do not make stereoviews of my own. So, back around 2008 I was going through the house, looking for things to sell.  Since I have not used this viewer for 4 years, I pulled it out to sell it. I did a bit of research and found 2 units sold with the last year for about $800. I decided to test the viewer, and looked at some stereoviews that I was selling on ebay. 

I WAS IMMEDIATELY  BLOWN OUT OF THE WATER!!!

The amount of detail I could see was just astonishing! I have a couple of stereoviews showing stereo cameras or stereoscopic equipment, but I could not see much detail, even though I was using a top-of-the-line stereoscope with achromatic lenses.  Everything was clear and right there with this viewer. I could see the MAXIMUM AMOUNT OF DETAILS!  It was a pure joy!

My immediate thought was "I am not selling this treasure".  There is no other stereoscope in the world that shows this amount of detail.  Not only that, but the lenses' spacing is adjustable, so I can fuse all stereoviews (except for the totally-mismounted ones).  Despite the very high magnification, this viewer is the most comfortable to use.

Why is this stereoscopic viewer so good?

The power of this viewer comes from the 100mm FL lenses which is about half the FL of standard stereoview lenses.  Magnification ~ 1/FL, so the shorter the FL, the higher the magnification. I don't know of any other stereoscope with higher magnification (correct me if I am wrong).

The lenses are achromats.  But, there is the trick: They are not prismatic.  But how it is possible to view 3" (80mm) separated stereoviews with our only 65mm separated eyes, without using prismatic lenses?  The answer is to have large enough lenses with adjustable interocular (distance).  And this is exactly what we have here.

Look at the pictures.  The lenses are held in a way that can be shifted, independently and by hand.  Very primitive, but you know what, IT WORKS!

The two knobs that you see on each side of the lens board adjust the distance of the lens board to the stereoview, so they are used for focusing.  Independent focusing at each side... that's new!

The light is provided by a fluorescent bulb.  It is bright and diffused.  The stereoview is inserted as seen and it just sits in place.  The viewer is rather heavy, thanks to anodized (black) machined metal.  The two handles are just great!  They allow you to hold the viewer comfortably in your lap.

I was wondering... Since this is basically a simple viewer, does it have to be so large and so heavy?  But it works surprisingly well.  John Dukes has designed a no-nonsense devices, simple, yet solid and very effective. It does the job with flying colors.

How many of these were made?

I believe around 100.  The serial number in the one pictured here is 145  (the numbering started at 100, not 1)... That's all for now. If I learn something new about this viewer, I will update the information here.

Keystone Visual Survey Telebinocular Achromatic Stereoscope

From all possible optical aberrations, chromatic aberration is perhaps the one that bothers me the most!  Thankfully, a good stereo Realist format viewer (like my favorite, the Realist red button viewer) with achromatic lenses shows no chromatic aberration (except for the Kodaslide II, see my blog here). To check for chromatic aberration, just look through the viewer with no slide and pay attention to the edges. Do you see orange and blue colors? This is chromatic aberration.

Stereoscopes (for vintage 7 inch wide stereoviews) show chromatic aberration because they use prismatic lenses. Prisms (essentially asymmetric lenses) bend the light more than symmetric lenses and different colors tend to be separated more, hence the aberration shows up more easily. But still, not many people notice this, maybe because they do not know what to look for. But you should be able to tell when you use a stereoscope with achromatic lenses.  One of them is the Keystone Visual Survey Telebinocular, used for eye testing in the early 1900s (maybe up to the 1960s or 70s?). These have different model numbers like this one, labeled 46C Ophthalmic Telebinocular:

I remember how I got my first Keystone Visual Survey stereoscope (pictured above). I recorded the story in a photo-3d posting: A friend from photo-3d offered to sell me this stereoscope for a little over $100, back in 2000 or earlier. I accepted but felt that I was doing him a favor and wasting my money because I already had some very nice stereoscopes at home. Perhaps I could sell it and break even, I thought. The stereoscope arrived; I opened the box and took a look. "Ugly duck" was my first thought. I decided to give it a try. Grabbed a few stereo views and took a look.

Wait!!! Just a minute!!! What is going on here??? There is something in the quality of the image that I have not seen before. Are my eyes being fooled? I ran to the basement and pulled out all my stereoscopes. I checked the same view with every stereoscope I owned, plus the Visual Survey. No, my eyes were not being fooled. The image through the VS looked better than anything else!!! No sign of chromatic aberration (I could see false colors in every other scope I tried). Sharper images. More details, especially at infinity. Easier for my eyes. I could be viewing for hours with no fatigue.

WOW! This baby is here to stay! I gave it a good TLC cleaning and have it in my basement ever since. Whenever I want to enjoy stereo views, this is the scope I use. Later, from discussions in photo-3d and input from Alan Lewis, I realized the secret behind the optical quality of this instrument: It has achromatic lenses! While every other scope has simple wedge lenses, this baby has achromatic lenses. I know from my slide viewer experience what difference achromatic lenses can make. The large size of the lenses and large FL makes this difference lens significant, but it is still there. And a trained eye can pick it up very easily.

Here is a comparison between the lenses of the Keystone VS Telebinocular, vs. a standard stereoscope:

The VS Telebinocular lenses are thicker (21mm vs. 7mm). If you take them out, it appears that these are halves of achromatic lenses. So, a standard stereoscope uses half of a standard one element lens, while an achromatic stereoscope uses half of an achromatic (two element) lens.

The bottom line: I sold all my other stereoscopes and kept this one.

But, it gets even better: Eventually, I bought a smaller stereoscope with achromatic lenses from Alan Lewis. It is called the “Achromat Lorgnette II”. It folds and can fit in my pocket. This is my preferred stereoscope, only because it is portable and I do not view stereoviews very often. Here it is:

A beautiful (made out of wood) portable achromatic stereoscope. I believe I paid around $300 for it in the early 2000s. Too bad it is not made any more.