Back at the beginning of the seventeenth century when Galileo invented the telescope, two were put side by side and the modern day binoculars were invented. The Galilean design is still used today for the less expensive versions and has some limitations in terms of its magnification capabilities.
An improvement to the Galilean design was done in 1611 by a man named Johannes Kepler. His method meant that higher magnification was possible. Using the Keplerian telescope design had its own problems as the image you viewed appeared inverted but there were various ways to get around this.
An Italian named Ignazio Porro patented a method of correcting the image correction in the middle of the nineteenth century which was improved further by manufacturers Carl Zeiss. Carl Zeiss used the Prism design and improved it in 1890 and were successful lens manufacturers and are even still around today. Having has a double Z shape set up to correct the image inversion and because of the added width of the unit it had improved depth perception.
A big use for these type of products was the opera which normally meant that they were of a fixed magnification variety. Other uses that required different levels of magnification meant that there was a need to improve the way in which the magnification was changed. Traditionally both eyes had their own way of adjusting the magnification which was separate and independent from the other.
Their use was becoming more and more widespread especially for use in the field by the military. To make them more practical for use in the field they were fitted with a central focusing adjuster. With one movement both tubes could be focused at the same time resulting in much quicker vision of far off subjects. Once the individual tubes had been adjusted to meet the strength of each eye then the whole unit could be altered by turning one wheel. In terms of practical military use this meant that a massive increase in the advantage gained by their use.
Another method of changing the magnification is the zoom lens although these tend to be used in cameras. This uses a number of lenses that can be adjusted by the use of a zoom lever. The design is less practical as it is quite fragile. The zoom lens is also linked with eyestrain and fatigue of the eyes.
Today, Binoculars are often used by amateur astronomers and are good for spotting events like comets and other astrological events. They have a far greater range these days but those that are greater in size than 70mm are better for terrestrial viewing and it’s really when you go over the 90mm that astronomical users tend to utilize them.
Whether they are used by astronomers, the military or even just for ornithology then it’s pretty amazing that four hundred years later little has changed. Their success has been a credit to the early pioneers Galileo and Kepler. I wonder if the next four hundred years will produce much change in the way in which they are made.
Mike Davis owns a best binoculars blog. He reviews the best binoculars of many top brands and highly rated models such as Zeiss binoculars, Pentax binoculars, Bushnell binoculars and more.