After discussing a handful of topics regarding binoculars and spotting scopes, a particular topic that has always elicited interest among readers is lens coating. Its process of application, advantages, and lens coatings itself help companies to better market their products. It helps in creating curiosity among consumers. But the subject of lens coating can be really confusing, with it being too highly technical. A better understanding of the basics about spotting scopes and binoculars would be of great help for anyone who plans on buying one. But before that, we should first understand some concepts about light.
One should be knowledgeable about the Laws of Reflection, Refraction, and Light Transmission and their effects when light hits the lens of binoculars or spotting scopes. In the instance that a wave of light strikes a glass lens, the light may reflect, refract, and pass through it. That is why
it is a demanding work for opticians and physicists to make the appropriate balance of lenses and prisms within optical devices which have multiple lenses.
Everything that can be seen by the eyes is a composition of visible light waves. These waves pass from the outer surface of the objective lens and make their way to the opposite side of the eyepiece lens, and finally into the observer’s eyes, making it possible to see images. The colors of an object that we see are the color of light it reflects. Also, an image should be appropriately magnified to have a clear and sharp view of it.
During ancient times, Galileo had made a telescope which provided him a magnification of just almost 3x, and gave images that were far from being clear. If today’s scientists also had the same material Galileo used, which is the quartz crystal, then we probably would not have made any further progress and still would have been using that same kind of telescope. Luckily, today’s technology has provided us with a wide variety of glasses and other materials to choose from that are helpful in creating quality lenses. Also available are the different types of coatings that give a lot of great qualities and advantages.
Considering every substance out of which a lens can be created displays particular qualities, a particular effect can be produced upon having that substance comes in contact with a visible wave of light. Here is where coatings can be of great use. When applied to lenses and prisms, coatings can be used to either enhance or lessen those effects depending on what is desired. But why not just choose a specific material that caters to the desired effect? That’s because even if a particular lens material have the desired light management characteristic to achieve a certain effect, it may lack other important qualities like durability, and perhaps it would not be pocket-friendly. Coatings, however, can produce similar effects when properly applied to a lens material.
An average person is mostly exposed with “metallic coatings”. This type of coating is used to convert glasses into mirrors. Metallic coating, when applied to glass or other materials, is of big help in making binoculars and spotting scopes maximize the amount of visible light they can reflect. Commonly applied on one or more surfaces of a roof prism assembly, it prevents the light from passing through the surface of the prism, and diverting it towards the direction of another surface. Due to their unique ability to efficiently reflect light, aluminum and silver are the most commonly used substances in metallic coatings. Other materials which can also be used are gold and copper.
In addition to metallic coating, the other kind of lens coating used in binoculars and spotting scopes is “multicoating”. As its name suggests, a multicoating is made up of multiple layers of coating applied to a surface. Unlike metallic coatings, multicoating aims to reduce the amount of reflected light that comes in contact with the lens, allowing more visible light to pass through it. This improves the efficiency of the optical device since less light is lost. Although multicoating is often beneficial, sometimes, the use of a single-layer coating is recommended for achieving a specific purpose. The important thing to remember is to apply the appropriate coating designed for a particular lens. This, together with proper positioning in the optical system, would result in attaining the required effect on the light.
Multicoating uses inorganic compounds like magnesium fluoride and calcium fluoride, and few other substances. Aside from minimizing the amount of reflected light in lenses, multicoating is also used to divert the direction into where light refracts when it passes through the lens. By reducing the amount of the separation of visible light, these coatings, with the help of the substances found in the lens, prevent the image from getting distorted and from losing its clarity and sharpness when seen by the viewer.
Lately, a certain type of coating has caught the biggest media attention, it is called “phase coating”. Phase coating is applied to the roof prism in binoculars or spotting scopes, securing that when the image leaves the prism assembly, it will not get distorted or altered upon making its way in the wave of visible light. Roof prisms were developed to allow a long optical path to be contained in a minimal space, but they have the tendency to disorganize the image which is composed of visible light by splitting and rebuilding it with the longer wavelengths inconsistent with the shorter wavelengths. Phase coating keeps it from happening by manipulating the speed of a portion of the split light waves so it is in accordance with the rest when they exit the prism.
Recently, a variety of new types of coatings has been developed to avoid accumulation of dust and water drops on lenses. A good example is the Swaroclean coating which is applied on Swarovski binoculars and spotting scopes. The surface energy is lessen upon the application of the coating. This makes the lenses to resist dust, water and other residue, making them a lot easier to cleaner when needed.
Zeiss has also developed LotuTec, a coat they apply to their products. It specializes in repelling water, mist and grease so they form small droplets on the surface of the lens instead of sheeting. Tiny droplets have less surface adhesion compared to water sheets, so they are easier to remove off the lens, keeping the lens clean and dry.
These are just a few basic information about lens coating, there’s a lot more to learn. But these are enough to equip you with useful information you need when buying binoculars or spotting scopes.
