Calling for a new wideangle binocular

"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:

• The manufacturers increasingly focused on the requirements of the birder as a customer: The birder does not, in general, require super-wide views, but focuses on a particular subject near the center of field. It is the observation of details, rather than surveillance or the inspection of a scenery in its whole which is the birder's task.
• Wide angles are tough: Optical aberrations increase rapidly with the angle of view, and even a sophisticated design leaves a lot for the amateur optics tester to pick at and complain about ("poor edge-sharpness!") on the Internet discussion boards - something no high-end manufacturer likes to read about his product.
• Wide angles are heavy: Prism-size, eyepiece-size - everything turns XXL, and during times in which small and slim is "sexy", every marketing expert may be having nightmares when considering the task of selling 1kg bricks of glass and metal to his customers.

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

• Our eyes are wideangle instruments - it is natural to leave as much of that as possible during visual observation through a binocular. It makes the fundamental difference between watching an event trough an instrument or becoming an integrated part of that event.
• Binocular observation is much more than just observing details near the center of field. Astronomers enjoy sweeping through the Milky-Way with wideangle instruments, travelers like to pan over landscapes at scenic spots, geologists like to study geological formations in their environmental context.
• Most significantly: We now have reached a technological level that allows us to combine wide fields of view with high image quality and comfort of view.

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:

• 8x40 is the ideal all-purpose format, with 5mm exit pupil being suitable for a wide range of applications, with 8x comfortably hand held, and with 40mm lenses small enough to enable the implementation of very wide angles without turning excessively heavy.
• 16mm eye-relief allows for a comfortable view and at the same time delivers a manageable eyepiece size. The eyepiece-lens that faces the eye will have a diameter of just below 30mm, and there remains space for the nose in between both oculars.
• The instrument, if made with Porro prisms, would have a weight of roughly 1kg and would probably cost between 1000 and 1500 Euro if made in Japan. Remind, for comparison, the 10x50 Fujinon FMTR-SX which has 65 degs. field, oculars with field flattener and high edge-sharpness, with a price-tag about 750 US$.
• If made as a roof prism binocular, such an instrument would possibly weight roughly 850g, but its price would reach or exceed that of existing premium roof binoculars.
• Even hybrid prism-mirror designs as employed before with the Leitz Amplivid of the 1960s are now thinkable. Leitz abandoned that design, also because the mirrors of those days, made of aluminum, easily lost their reflectivity. Today's dielectric mirrors have a reflectivity near 100% and come with unlimited lifetime.