When analyzing the term binocular, one discovers that it is a compound word that results from the union of two Latin words: binus (translated into Spanish as “double”) and ocularis (interpreted as “ocular”). The concept, therefore, refers to what demands the attention of both eyes at the same time.
The term of binocular, as many of you will know, is intended to identify the optical element that allows you to look or observe simultaneously with both eyes. Binoculars are also known as binoculars or riflescopes and their function is to increase the image of objects that are not so close that can be seen through the device.
The telescope and monocular are other optical instruments that magnify images. The main difference with binoculars is that they generate the effect of stereoscopy (that is, they recreate the illusion of depth in the image). Stereoscopy is achieved thanks to the fact that each of the two tubes of the binocular contains different lenses and a prism, which allows to enlarge the image for each eye in particular.
The light passes through the series of lenses until it reaches the prisms, which are responsible for placing the image in its correct position through the principle of total internal reflection. This also differentiates binoculars from telescopes, which display the image reversed.
It should be noted that there are multiple models and types of binoculars. Most of them offer the possibility for the user to adjust the separation between the eyepieces for greater comfort. Binoculars also often have a diopter correction ring (installed on the right eyepiece to improve focus) and include focus wheels.
The magnification of the images and the diameter of the target is measured in millimeters, and is expressed with a pair of digits that are separated by an X. Binoculars 14 × 60, for example, offer a level of magnification of 14 and a pair of goals 60 millimeters in diameter.
Tips for choosing the ideal binocular
To find out what is the magnification of a binocular, just pay attention to the first figure that appears in its measurement; If you have a 10 × 50 device, it means that you can enlarge or reduce the size of the object up to 10 times. In other words, if with it we are going to observe the Moon, which is located at a distance of 384,000 km, we will see it as if we were at a difference of 38,400 km.
Regarding the visual field, this data indicates the angular size allowed by the device. If you have a 7º field of view, you can see objects that may be within a 7º diameter. It is worth mentioning that some models refer to the visual field in feet or meters; that is, in a straight line. Both values are important and that is why it is good to know how much of one is the value of the other. For example, if the binocular has a field of view of 373 feet, its equivalent in degrees is 7.1º. It is calculated through the following formula: C (visual field in degrees) [º] = Arctg (L (linear visual field) / 914m (linear field constant).
Other fundamental aspects to take into account when choosing the ideal binoculars are:
* The aperture: indicates the amount of light that enters; the greater this, the more detail can be achieved in visibility;
* Magnification: indicates the level of zoom in or out that can be achieved; the higher this value, the smaller the field of visibility. This detail must be considered taking into account the opening; it is necessary to find a balance between both values;
* Exit pupil: refers to the diameter of the light beam emitted by each eyepiece and is measured in millimeters. It is extremely important to take it into account, especially for binoculars that will be used innight observation;
* Eye and focus adjustments: those devices that are more malleable and that allow customizing the focus and the observing eye are the most recommended, due to their versatility; however, it is always advisable to be clear about the use of the binocular to know which device to choose.