Calling for a new wideangle binocular

by Holger Merlitz

"The binocular market is offering everything that could possibly sell. If there would exist any additional niche, promising enough to make money with, then the manufacturers would have already jumped on it"

This is the standard counter-argument one is facing when suggesting a new product. Since we have a free market, everything that possibly makes money already exists and hence there is no need for any suggestions. That sounds odd, and in fact, concerning the present binocular market, it is.

8x40 wideangle of ancient times, by Pentax: Fun to use, but far from being high-end

Many binocular users are aware of the absence of true wideangle instruments in the high-end sector. While, during the 1960s and 1970s, there were plenty of super-wideangle binoculars made in Japan and sold all over the world, those had never been of premium quality and by now they have essentially disappeared from the store's shelves. Premium wideangle binoculars were made during short periods in the 1950s and 1960s, by Leitz, and then quickly disappeared from the high end market. Why is that so? The main reasons are:

Yet, there exist good arguments in favor of a new and high quality wideangle binocular. These are

In what follows I want to focus on the last point. One has to bear in mind that during the 1960s and 1970s, toward the end of the "golden age of wideangle binocular construction" as stated by Fan Tao, the technology of eyepiece design was still on the level of the 1920s, with variations of the Erfle-design all over the place and nothing much else. Those were fine up to apparent angles of view about 65 degs, and were certainly overstretched when applied to angles beyond 70 degs. Additionally, those eyepieces had a poor eye-relief, hence were impossible to be used with glasses and still inconvenient without.

Left: Modified Erfle eyepiece. Right: Nagler eyepiece (US patent 4747675, 1988)

With the dramatic improvements in eyepiece design, triggered by the Naglers during the 1980s and thereafter, the situation has changed entirely. The construction of a high quality eyepiece with 75 degs field, which remains sufficiently compact to be used in a binocular, and which offers a reasonable eye-relief for viewing comfort, has become possible. Those oculars contain field-flattener ("Smyth-") lenses that significantly increase eye-relief, and at the same time reduce field-curvature and improve edge-sharpness.

Another significant improvement since the 1980s was the development of low-dispersion ("ED"-) glasses that revolutionized the objective designs of premium binoculars. Nowadays, ED triplets are capable of delivering image qualities far off the center of field that were unheard of a couple of decades ago.

Finally, coating technology has advanced a lot in recent years, allowing for a wider range of optical designs without excessive loss of transmission or the danger of emerging stray light.

So, what then would be a reasonable proposal for a modern wide-angle binocular? My suggestion is an 8x40 binocular with 75 degs. apparent angle of field and eye-relief of 16mm. Why would I suggest that, and how did I come to these numbers? The answers are:

In the past, there have been super-wideangle binoculars of the 8x40 format, for example the Zeiss Deltarem and the Huet roof binoculars, both with almost 90 degs. fields. However, these designs were surely overstretched, with very poor edge-sharpness and, necessarily, short eye-relief (the eyepiece diameter scales proportional with the eye-relief and the tangent of the apparent half-angle of view). Stopped down to 75 degs., combined with present time technology, such a design would now become manageable, including high image quality and viewing comfort.

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Last modified: Jan 2012