How are binoculars described?
Binoculars are described using two numbers, such as 7x50 or 8x25. The first number describes the magnification. The second is the diameter of the objective lens in millimetres. Magnification power describes how much closer objects appear when you view them. In 7x50 binoculars, the image is magnified sevenfold. Increased magnification reduces the brightness of the image, so as the magnification increases, binoculars require increasingly larger objective lenses to maintain overall brightness. The larger their size, the more light they can gather.
"The magnification of marine binoculars should not be too large."
Binoculars for bird watching or stargazing offer too much magnification for use on board. The more an object is enlarged, the more difficult it is to keep it in view, therefore a magnification of x7 is ideal for use on vessels with a length of up to 15 meters.
Binoculars with 7x magnification
What features should marine binoculars have?
Marine binoculars are more prone to exposure to the elements than conventional models. Binoculars can also easily fall off of surfaces or out of your hands in rough conditions at sea. Water exposure is also an issue when using binoculars in a marine setting, so getting a pair which is water-resistant or at least water-repellent is definitely worth considering.
"Waterproof binoculars are a must for any water sports enthusiast!"
Binoculars used on water are always exposed to very high humidity and splashing water. In combination with constantly changing temperatures, the lenses can quickly fog up internally and externally, rendering them unusable. For this reason, waterproof housing with an inner O-ring, filled with nitrogen, protects your binoculars from moisture and the ingress of water. In any case, our SVB experts recommend that you purchase waterproof binoculars, such as those made by Marke SEATEC, especially if they are to be used regularly in marine environments.
What are the advantages of marine binoculars with an integrated compass?
Built-in compasses which appear superimposed on the lens allow the user to take on the course of an object which would not be visible on a set of conventional binoculars. Binoculars with an integrated compass can be very helpful when navigating on board of a vessel. If you are faced with the choice between: binoculars with a compass or binoculars without a compass, our SVB experts recommend that you always purchase the version with a compass when the binoculars are to be used in an active environment.
What is an eyepiece focus?
Binoculars can have independent eyepiece focus, which compensates for the differences between the eyes of different users and changing distances between the user and the object. For center-focusing binoculars, the eyepiece can be adjusted to compensate for your individual eye strength. After your individual eyes have been set into focus, a focus knob is used to uniformly adjust the distance of both sides.
How much do marine binoculars cost?
The SVB Shop and the SVB catalogue both offer a wide range of binoculars, from entry-level models, mid-range models, such as our SEATEC binoculars and more expensive, high-end professional units from Fujinon. Prices range considerably, from under €40 to several thousand euros. In general: Great binoculars with brilliant, contrast-rich images are quite expensive, but their incredible functionality and performance pays off! For maximum optical performance and robust mechanics, which also withstand moisture, cold and heat, we recommend choosing one of the high-end binoculars. The differences between premium binoculars and lower-end models are truly remarkable, making spending the extra money absolutely worthwhile in the long run.
What is the relative brightness of an image and why is it important?
The relative brightness of a binoculars’ image is an indication of the functionality
of the optics. Having a high level of brightness is particularly important in twilight. The
brightness can be calculated with the help of the binoculars’ dimensions: (lens diameter /
magnification)². It’s evident that a larger lens provides greater brightness: a binocular with a
lens diameter of 30 has a brightness of 18.3 ((30/7)² = 18.3), while a binocular with a lens
diameter of 50 has a brightness of 50 ((50/7)² = 50)! In this case, the relative brightness of the
image is increased by 177%! It is therefore worth investing in a higher-end set of binoculars with
larger lenses, in order to benefit from a higher degree of brightness which will in turn improve
image quality in any situation.
Cheap and poor-quality lenses don’t allow as much light to reach your eyes – usually only about 70 - 75% of the total amount. Top models by FUJINON let much more light pass through! These binoculars allow up to 97% of incident light pass through the lens, which means that objects are displayed much brighter and sharper compared to cheaper lenses. This not only facilitates improved sight, but it also makes your eyes less prone to fatigue.
Why the twilight factor in binoculars is important and how to calculate it?
The twilight value indicates how bright a pair of binoculars is at dusk. The higher the twilight factor, the more details are visible even in poor lighting conditions. The twilight factor for binoculars is calculated as follows: √(magnification x objective diameter). Binoculars with a magnification of 8 and an objective diameter of 42 mm thus have a twilight value of 18.3 (8x42 = 336. √336 = 18.3). In a country like Germany, in which the twilight period is long, it makes sense to opt for binoculars with a high twilight value. In other countries, where the twilight period is short, the light intensity and brightness of binoculars play a greater role.
What effect does the coating of the objective lenses have on the quality of binoculars?
Binoculars’ lenses receive a chemical coating during the manufacturing process, which not only protects them against scratches, but also reduces the effects of reflections, thus increasing overall light transmission. This coating is noticeable by its distinct colouration. The less colour you can see, the better the coating generally is. When light reaches the binoculars, between 5 and 10% of it is reflected away by the glass, which consequently does not penetrate the eye of the user, thus making objects appear less bright with poorer contrast and clarity. Ultimately, having a high quality coating on your binoculars makes it possible to reduce the amount of reflection significant.
The use of state-of-the-art materials is setting new standards in optical performance and durability.
Written by our SVB (technical) experts
Our team of SVB technical experts is there to give our customers professional advice on all matters relating to technology on board. Their expertise is the result of regular training and many years of experience.