What is magnification?
Magnification in binoculars describes how much closer an object appears compared to what you see with the naked eye. A 1x view is life-size, showing the scene exactly as your eyes see it. 2x magnification makes objects appear twice as close, 4x makes them four times closer, and 8x, as in many general-purpose binoculars makes them appear eight times closer. While higher magnification brings more distant objects into view, it also narrows the field of vision and can make the image shakier without a tripod or steady hands. The key is finding the right balance between magnification, brightness, and stability for your own viewing needs.
Optical Brightness
In binoculars, it refers to how bright the viewed image appears and is mainly determined by the size of the objective lenses and the magnification. Larger objective lenses gather more light, making the image appear brighter, especially in low-light conditions. Magnification affects the size of the exit pupil (the beam of light leaving the eyepiece), which is found by dividing the objective diameter by the magnification, a larger exit pupil generally means a brighter image. The twilight factor combines both magnification and lens size to indicate how well the binoculars perform in dim light, such as at dawn or dusk.
What is the field of view?
Field of view (FOV) describes how wide an area you can see through the optics, usually measured in degrees or metres at 1.000 meters. A wide field of view means you can see more of the scene at once, which makes it easier to locate and track moving subjects like birds and other wildlife. It also gives a more immersive, natural viewing experience. While higher magnification tends to narrow the field of view, models designed with wide-angle optics balance this by keeping the image open and easy to scan, which makes it ideal for spotting, observing, or following action in dynamic environments.
Transmission and colour reproduction
Light transmission refers to how efficiently a binocular or spotting scope passes light through its lenses and prisms to your eyes. The visible spectrum covers wavelengths from roughly 400 to 700 nanometres, which includes all the colours we can see, from violet through to red. High-quality optics aim for even, high transmission across the entire visible spectrum, ensuring that all colours are transmitted equally and the resulting image appears bright, sharp, and true to life. If transmission favours certain wavelengths more than others - for example, boosting reds or muting blues - the image can take on an unnatural colour tint. Therefore, consistent light transmission across all visible wavelengths is essential for achieving natural, balanced colour reproduction and accurate viewing.
Chromatic aberration
Chromatic aberration, often seen as colour blur or fringing, occurs when different wavelengths of light (colours) do not focus at the same point after passing through a lens. This happens because glass bends each colour of light by a slightly different amount, for example, blue light refracts more than red. The result is faint purple, blue, or green edges around high-contrast areas in the image, reducing sharpness and colour accuracy. To combat this, optical manufacturers use special low-dispersion glass or advanced lens materials that better align all colours into a single focal point. Kowa PROMINAR fluorite crystal lenses are among the most effective solutions, as fluorite has exceptional light dispersion control. This material virtually eliminates chromatic aberration, delivering images with outstanding sharpness, natural colour, and high contrast, even at high magnifications.
Optical coatings
Optical coatings are ultra-thin layers applied to the surfaces of lenses and prisms inside binoculars and spotting scopes to improve image quality. When light passes through uncoated glass, some of it reflects off the surfaces, reducing brightness and contrast. Coatings help minimise reflection and maximise light transmission, resulting in a brighter, sharper, and more colour-accurate image.
There are several types of coatings:
• Coated optics have a single layer on at least one lens surface to reduce glare.
• Fully coated means all air-to-glass surfaces have a single coating.
• Multi-coated optics have multiple layers on one or more surfaces for better light transmission.
• Fully multi-coated optics, found in premium instruments, have multiple layers on every surface, delivering the highest brightness, contrast, and colour fidelity.
High-quality coatings such as Kowa's KR coating can also protect lenses from scratches, moisture, and dirt, ensuring durable performance in all conditions.
