The first thing you need to know about your pair of binoculars is that they are basically derived from a classical telescope that has two lenses. The lens that is nearest the object hat you want to view, also known as the objective lens is what provides the image before it is enlarged by the lens that is next to your eyes, also known as the eyepiece lens; it can be moved closer or further away from the objective lens. Essentially therefore, your birdwatching binoculars can be seen as two telescopes that have been laid side by side that will work together to produce an image with a depth of field as opposed to a flat image.
Light is refracted as it is directed through the lenses such that by the time it comes to the viewer’s eyes; the image will usually be upside down and back to front. This is normally corrected by two prisms that are placed between the eyepiece and the objective lens inside the binoculars. These four prisms found in the shoulders of the binoculars are what give them the typical squat appearance.
Power, light and weight: The power of your birding binoculars will be expressed as two numbers such as 8×42. The first number refers to the times magnification while the second number refers to the diameter of the objective lens. A binocular with a larger objective lens will make more sense when it is used in low light conditions because of its ability to capture more light. The magnification factor indicates the number of times the object will get magnified and inmost applications the number is between 4 and 8; any binocular with magnification larger than 9 and 10 will magnify even the slightest shake of the user’s hands and will make it difficult for the image to be seen.
Glass coating: Naturally, glass tends to reflect up to 5% of the light that hits its surface back to the source. Manufacturers have designed coatings that can easily prevent this because they allow more light to pass through the lens and very little if any gets reflected back. Since its advent, the coatings have continued to get improved so that today there are several grades of coating. Multiple layers of coating will give the best results and they are usually applied to the front and rear lenses.
Price Justification: When people are selecting birdwatching binoculars one of the most important considerations is the price. The price will be affected by numerous factors. The first important one is the type of lens as well as the coatings that have been used. Glass lenses coated on both sides using multiple layers deliver pictures at the highest magnification and which a brighter and clearer than those produced by plastic lenses. The quality of the build will also affect the price such that those that are more rugged and can be sued in harsh conditions will be more expensive.