Because of the short tubes, early binoculars were constructed with the Galilean lens arrangement and are called Galilean-type binoculars. The double-convex objective and double-concave eyepiece, results in powers little better than 3 to 4x., providing an inferior contender to the multi-lens, higher power terrestrial telescopes. It wasn’t until the late 1800s when creative designs began to appear and people began to appreciate the compactness and convenience of binoculars that they were produced in quantity as ‘field glasses’. For example, in the 1880s ‘telescoping’ binoculars with 4 lenses in the eyepiece tube were offered. These long binoculars are basically two Schyrle-type telescopes mounted in parallel. Some are large but lightweight, with aluminium bodies, and can magnify up to 16x. They were popular in the military during the World Wars. By the late 1800s refinements on some binoculars included sling loops for straps, sunshade cylinders and hinged bridges or ‘bosses’ to adjust for differences in eye separation from user to user. Aluminium construction rather than heavier brass was becoming more common.

The original opera glass was designed in the early 1700s as a simple small monocular telescope based on the Galilean two-lens system. The first binocular opera glass was introduced in 1823 and consisted of two small telescopes joined by a stationary bridge with each side focused independently. Typically, opera glasses only focus 2 to 3x. They were intended from the start to be elegant works of art and many are ornately decorated with enamel scenes or gilded with gold. Some are clad in silver, pewter, ivory, tortoise shell or mother-of-pearl and some are attached to a telescoping hand hold called a ‘Lorgnette handle’. Most opera glasses come in plush silk-lined leather cases or silk draw-string bags.

Although the technology had been available for some time, it wasn’t until nearly the turn of the century that a truly successful prismatic binocular was developed. In 1894, Professor Ernst Abbe teamed up with the Zeiss Company to produce the Feldstecher (German for field glass), using Porro prisms. The largest model magnified to 8x. It has individual screw focusing eyepieces and a hinged bridge connecting the two tubes, thus is adjustable for eye separation. Prismatic optics revolutionized the binocular by using two prisms back to back or other arrangements of prisms to rebound light and effectively extend the distance between objective and eyepiece thus compacting the tube while at the same time increasing the ratio of focal lengths between the two lenses, resulting in higher magnification. The prisms also widen the distance between objective lenses thus enhancing the stereographic perspective or perception of depth. By 1910 binoculars were produced in large quantity for both military and civilian use in several countries and invariable come with leather sling cases. Binoculars became more diverse and large, heavy, rugged brass binoculars made for navy boat decks contrast with small, dainty feminine opera glasses. Illumination and brightness were greatly improved in the 1930s when a thin coat of magnesium fluoride was applied to glass surfaces to reduce distracting reflections.