The popularity of the brand and model simply help us to choose a binocular. But there are some fundamental issues to be taken in consideration to choose the best one for you. Especially the working process and the meaning of marked numbers on the binocular are still unknown issues to many of us. Let’s continue reading the article to know the details as much as possible before making your decision to choose the right binocular for you.
What is binocular and how does it work?
To state the working principle of binocular, we can tell it as the working item that uses a series of lenses, prisms and other some passive elements with a view to generate magnified view of remote objects.
Telescope requires you one eye closed when viewing objects over the device. But binocular has two parallel tubes based on the same technology that really makes our viewing system more comfortable. Viewing over the both eyes makes the object easier to be viewed in 3-D appearance.
The physical view of the binocular varies by the type of lenses and prisms used in it. The horizontal and vertical view together forms the natural view of an object. Without the presence of the prisms the binocular makes things upside down and distorted. Check this article to know the description and usage of binocular.
Binocular Prism: roof and Porro
Prisms used in the binocular are generally classified by two types roof and Porro. For the roof prism, Glass elements are structured by front to front. This organization makes the binocular easier to hold and well structured. Porro prisms glass elements are counterbalanced that makes the view easier for the wide range of objects. The difference can be distinguished by the light path. Light path makes the length shorter and makes the object separate when viewing over the binocular.
Why the prices of binoculars vary?
The prices of the same looking binocular may vary ranging from 20$ to nearly $3200. The quality of the lenses and prism is the main reason of that variation in price. A pair of Porro and roof binoculars may be same in looking but they are different when considering the issues of quality and performance. Roof prism containing binocular is more expensive compared to porro. Budget should be taken as considering issue when choosing your binocular.
In some binoculars, the double-Porro prism is used but they are generally called by just “Porro”. SIgnazio Porro invented the prism system in 1850. In binocular, Porro is taken from the last name of the inventor. Binocular is the double-Porro prism technically but is it known as just “Porro”.
The working principal of the prism can be described as the point from where the light exits and enters into the prism. That point is generally called by folded light path.
Roof prism first flipped up and corrected the image both in vertically and horizontally and created required object at the straight point of folded light path. Roof prism was used in Abbe-Koenig (AK). AK prism setup is commonly used in binocular but there are variations in the AK setup. Other AK design includes Schmidt-Pechan (SP) and Amici. These binoculars conduct the same work but in different ways. The objects are formed by the different optical routes of the lights for different designs. SP system constructs more compressed image or object compared to the Amici and AK prisms. That is the main benefit of the SP based binocular. The compact object can easily be processed by thinner optical tubes which can easily be hold.
Pro Tips:
Roof prisms are costly compared to the Porro prism binoculars. But we can get higher quality Porro prism binocular with the same price of roof binocular.
Essential terms for binocular: what we need to know
The properties of a binocular can be defined by a number pattern like 20×70. The first term 20x defines the magnification power and second term 70 refers the diameter of the object. The 20x means that the binocular can make the object 20 times closer than viewing the object by the naked eye. Generally 10x zooming system serve the basic purposes. If you want to enjoy the game in football playground then you can choose 7x feature. In some cases, using binocular more than 10x system may cause difficulties to use in long range.
The magnification is inversely proportional to the field view. If the magnification is higher, the viewing area will be smaller.
The number 70 of the format of 20×70 means the diameter in millimeters of the front lens.
The weight and size of the binocular depends on the space taken by the objectives. The amount of light gathered by the binocular is also a reason of the size of the binocular. Simply, smaller lenses will pass lower light than the larger lenses. Object of image created by the larger lenses will be clearer, brighter and sharper. Size and weight are two factors should be taken in consideration when choosing one because using the binocular comfortably is important too.
The weight and size of the binocular depends on the space taken by the objectives. The amount of light gathered by the binocular is also a reason of the size of the binocular. Simply, smaller lenses will pass lower light than the larger lenses. Object of image created by the larger lenses will be clearer, brighter and sharper. Size and weight are two factors should be taken in consideration when choosing one because using the binocular comfortably is important too.
Variable magnification system is the new feature of the modern binocular. Suppose 5-40×70 is a feature or it is marked on a binocular. Here the tool features magnification from lower 5x level to the higher 40x level.
There are some binocular models those have a wheel or a thumb level so that the magnification can be controlled by that wheel or thumb level. In that case, user doesn’t need to change the grip. Zoom features actually gives the user flexibility but the sharpness and brightness may be decreased by zooming. The prisms and light processing are adjusted in such way that moving away from magnification may affect the quality of the object created by the binocular.
Prism image
Prism works like a mirror that is kept inside the binocular. It has both reflection and refraction capacity. For that reason, it’s refraction quality appears the object is such way that the viewer can see that in his own eye. For the refraction function, the newly created image is upside down and downside up. As the prism is an angularly slopped glass in shape, it inverts the objects back to its original format.
BAK-4 prism is made by quality glass materials and constructs quality image object in binocular. Phase coated prisms increase the contrast and resolution of the image object created in binocular. For that reason, that type of prisms are generally used in the expensive binoculars.
What does “Exit Pupil” mean?
Exit Pupil is nothing but the amount of focused light that is visible when viewer looks though the binocular. The exit pupil defines the quality of viewing experience in dim light. To check the exit pupil, you have to hold the binocular seven to ten inches far from the eye, and then you will see small dots light in the center portion of the eyepiece. The pupil of the eye is smaller than the diameter of the exit pupil.
For the human eye, the pupil varies from 1.5 millimeter to 8 millimeter where 1.5 is for the bright environment and 8 is for the darker environment.
In the dark or low light condition human eyes’ open up to 8mm or 5mm in width so that extended pupil can pass more light through it. For that reason, we need similar valued exit pupil when using binocular in low light condition. In that case the pupils are adjusted to 2mm to 3mm so that extra transmitted light is not required.
The diameter of the exit pupil is calculated by the division of the objective by the magnification. The binocular marked by 10×41 contains the exit pupil of the 4.1mm diameter. But the binocular containing 10×25 has the exit pupil of 2.5mm. The 2.5 will be lower in quality than the average. So, viewing experience over the 10×41 will be better compared to the 10×25.
What type of lens should you choose?
The sizes of the lenses are calculated by millimeters (mm). Human eye adjusts with the light condition and type of object. For the binocular marked with 7x magnification, you can consider a binocular having 35mm, marked something like 7×35. Generally larger lens passes larger amount of light. This issue can be taken in consideration when planning to use binocular in dark environment or in low light condition. Scientists are trying to make the size smaller with the same capacity.
Roof Prism System
Roof prism binoculars contain prisms organized close to one another. This arrangement allows the objective lenses assemble directly in a single line with the eyepiece. This makes the binocular efficient and smooth in its shape and working procedure. Here the prisms and lenses magnify the object and then correct the object (image) in the straight line.
Porro Prism System
Porro prism binoculars contain the front lense or objective is not equalized to the eyepiece. It is counterbalanced from the eyepiece. In Porro prism binoculars, the sensitivity is more accurate and provides wider field of view.
What does “field view” mean?
The area size that can be viewed over the binocular is called the field of view or simply field view. If you consider about the power of binocular, then you have to measure the field view capacity over the binocular. If the power of the binocular increases, the field view area decreases. That means the power of the binocular inversely proportional to the field view. In the binocular manual, you may get field view in degrees instead of using liner field view. In that case, you have to multiply field view by 52.5 in case you want to convert that angular field view to practical linear field.
What does “lens coatings” mean?
Did you ever look sun shining on a sea or lake? If your answer is “Yes” then I must admit that you saw a glare coming off the surface of water. In case the manufacturer of the binocular doesn’t use coating on the lenses then we have to face same problem in using that binocular. Generally, the expensive binoculars have multiple coating on the lenses. These quality coatings generate clearest and brightest images.
Generally there are four levels of coatings over the lenses. We can simply assume the coating operation or mechanism from the type name of the coating.
- Fully coated: a single coating over the surfaces on air-to-glass
- Multi coated: more than one coating over the one lens
- Fully multi coated: Multiple layers over the air-to-glass
Tips for the professional binocular users
Professionals like astronomers, hunters and birders have to use binocular that has magnification level in 8x level and the wide exit pupils should be 50mm around, like the pair 8×54.
If you are a boater then you should consider the above type of binoculars that will help you to view the objects in dark environment. Remember that the wide exit pupil helps minimizing disorientation created in binocular when using it on rolling water.
What is Eye Relief?
Eye Relief is the most comfortable distance from the eyepiece of viewer eye. It can also be defined as the distance from the focal point where light is passed through the eyepiece. What is eyepiece? Eyepiece is nothing but the ocular lens.
Manufacturers setup the eyecups after the eyepieces the user’s eye adjusts at the suitable distance from eyepieces. This setup makes the device comfortable for the eye. Some binoculars have extra adjustment system on the eyepieces so that we can adjust the focusing to the eye prescriptions and thereby the binocular can be used without glasses. Basic eyecups generally can be folded back so that we can place our eyeglass lenses near to ocular lens. There is another type of eyecups that is adjustable and has twist in and out system so that user can setup distance correctly.
This video explains binoculars Binoculars Eye Relief
Generally the field view is inversely proportional to the eye relief. So, binoculars that have longer eye relief should have smaller field view. You will get a binocular having shorter eye relief with the similar price. Remember to get a binocular having broad viewing area when choosing one. Now, you have to take your decision how much eye relief is essential for you. In some situations when field view is not a major issue then you can choose one that has more eye relief. It mainly depends on the field of usage.
Glass, Prisms and Coatings
The quality of the glass used in the binocular is really a concerning issue. General glass that is not polished correctly may cause imperfection in creating image object. It can also bend light oddy and the color maybe skewed up. The newly created image inside the binocular may be distorted at it’s edges.
Scientists have invented glass that has low dispersion. That type of glass theoretically transmits better light without bending. So the formed image contains higher contrast and sharpness.
You can see some binoculars marked with “Eco-glass”. That means the glass is ecologically friendly. Remember, neither this guarantee the image quality nor the better viewing experience. It just assures you that it will not create any chemical pollution when disposal of the device.
The materials used in the prisms are significantly responsible for the image quality. Barium Crown glass is known as BAK4 that is considered to be the very good type of prism material. Mainly lower critical angle and high refractive index are two symbols of quality materials. This system conducts better light transmission and lower loss of the light.
If you consider a binocular that assures good quality within your budget then you may have to choose a binocular having BK7 glass. BK7 glass is not the best but you’ll not be able to distinguish the quality from the best one, like BAK4. But binocular containing BAK4 type glass is expensive. BK7 type glass has good light transmission capacity with very limited internal imperfection.
How to Choose your Binoculars?
Follow the following basic steps to select a binocular.
- Select a binocular that has 7x to 10x magnification level to use for the general purpose.
- Choose high magnification to see objects at long range
- Chose large lense for viewing objects at low light environment, like for bird watching.
- Fix your budget and purpose to choose the suitable one for you
- Know basic properties of water proof and water resistance. Then choose one
- Select glass lenses for viewing quality images and choose plastic lenses for durability
- Understand the eyepieces. Normal range of eyepieces is 5 to 20 millimeters.
- Check the manufacturer’s reputation and product reviews of the customers.
Brief discussion
The binocular world is huge and expanding day by day. You will get a binocular based on your budget and purpose. In this article we just have introduced some technologies and terms that may be helpful for you when buying one. You know the quality of the optics of your binocular. After choosing a binocular for you, don’t forget to have the collection of the related accessories that may improve your viewing experience.
If we leave anything important, feel free to write your comment that may be helpful for others.