What is this article about?
Are you looking at buying your first binocular but lack the necessary information to make the decision on what you should look out for in a binocular? Or do you already have a collection of binoculars but wants to know more about features of your binoculars so as to be able to fully utilize what your binoculars can offer you?
If you are any of the above or just someone who is simply interested in knowing more about binoculars, this guide will provide you with all (if not most) of the essential information about binoculars.
Ok, let’s get to the basics
Binoculars, in their simplest form, are the optical instruments comprising of lenses for each of the eyes and used for viewing distant objects. From idyllic activity like bird watching to adrenaline pumping events like watching races from afar, they are used everywhere. Not to mention the opera binoculars that are popularly being used for watching opera.
In a theory, we can almost say that using a binocular is akin having 2 telescopes combined side by side, however, one of the main advantages of binoculars (some called it field glasses) over telescope is the capability to make full use of both eyes to present a more in-depth and more 3-D view of the surroundings.
1. Optic designs of Binoculars
The earliest binocular were invented in the seventeenth century, using Galilean Optics (where a concave objective is placed in front of a concave eyepiece). Since then, there have been several advancements in the technology in field glasses construction to provide improved images and higher magnification thus the usage of Galilean Optics has been greatly reduced – in fact, right now Galilean optics are used mainly for cheaper models binoculars and opera glass which doesn’t requires high magnification.
*Using Galilean Optics
Currently, in place of Galilean optics is the Keplerian optics (uses convex lens as the eyepiece instead of the concave lens) which allows higher magnification and better images. However, as the eyepiece is using a convex lens the images produced using Keplerian optics are inverted (upside down) and in order to get the image “un-inverted”, additional technology has to be deployed – using of prisms.
*Using Keplerian Optics
- Keplerian optics provides better image quality as well as higher magnification
- Cost of a pair of binocular using Gelilean optics is much lower than one that uses Keplieria optics.
Conclusion: Get a pair with keplerian optics if you requires higher (usually more than 5 x) magnification and better quality. Otherwise Galilean optics binoculars will be more cost saving).
2. Roof Prism and Porro Prism
Prism allows you to see a correctly oriented image (remember “un-inverted”?) when you look through a pair of binocular that makes use of Keplerian optics. In modern binoculars (that are employing Keplerian optics) they usually make use of either Roof Prism or Porro Prism to “un-invert” the image.
Porro prism was the standard until 1960s. It uses the double-Z-shape to present the erect image; as a result these binocular are bulkier in appearance.
Roof prisms was a newer technology invented in the 1960s. Its objective lenses are straight in line with the eye piece and hence the body of binoculars using roof prism tends to be slimmer. . The image produced by them is brighter than that of porro prism one. It is so because the roof prism uses silver surface which leads to 10- 15% reduction in the light transmission (this actually results in the images produced by roof prism to be less bright compared to one that is produced by porro prism).
- Size: Some folks might prefer a more compact binocular (roof prism) while some might finds the bulkier porro prism binoculars more sturdy hence it up to individual preference.
- Quality: Due to the more advance technology employed, the best roof prism binocular offers much higher image quality than what the best porro prism binocular can possibly offers.
- Price: If comparing binoculars have the same image quality (in the average to good range), a roof prism binocular is much more expensive than one that is using porro prism.
Conclusion: Choose a roof prism binocular if you are looking for a binocular with the highest possible image quality or if you like binoculars that are more compact. Otherwise, if you are looking for a binocular that offer average to good image quality, a porro prism binocular provides better value for dollars.
3. Specs of a Binocular
Apart from the optical design, there are various other specifications that we need to be aware of when choosing a binocular. Below are some of the basics that you should be aware of:
This is simply the ratio of the size of an object that we see that is being magnified. Eg, for a binocular with 8x magnification, the object when we viewed through the binocular is 8x bigger than what we see without the binocular (do note that for most binoculars, the level of magnification is fixed unless stated as a zooming binocular).
- How to tell what’s the magnification level of a binocular? All binoculars are described using a pair of numbers such as 7×50 or 15×80, which refers to their magnification and objective lens diameter (eg, for 7×50, 7 is the level of magnification and 50 is the objective lens diameter).
- There are some binoculars that offer variable magnification whereby users can zoom in/out using a thumb level or wheel fixed on the binocular. The description of these binoculars are usually something like 10-30×6, which means the magnification can be adjusted from 10x to 30x while the objective lens diameter is 60mm.
- It is recommended to use a tripod if the magnification is more than 12x, as the higher the magnification, the more unstable the image will be due to shaky hands.
ii. Objective lens Diameter
Objective lens diameter refers to the diameter of the objective lens (which is also known as the front lens), which determines the amount of light collected for the formation of the image. It is indicated on the binoculars by the respective number (eg, for a 7×50 binocular, its objective lens diameter is 50mm). If two binoculars have same magnification and quality, the one with the larger diameter will produces sharper and brighter image. However with a larger objective lens, the binocular will also be bulkier and heavier which should be a major consideration if you need to use the binocular for long period of time.
iii. Angle of view
Also known as field of view is a measurement of how wide an area is encompassed in the binocular view. It is usually expressed in two ways; as the width in feet at 1,000 yards, or in degrees of field. In very simple terms, the wider the angle of view, the more area you can see and a wider angle of view is particularly important when observing moving subjects like animals or birds or at sporting events.
iv. Exit Pupil
Exit pupil is basically responsible for the formation of the bright images even in the low light conditions. A larger number is preferred for getting a brighter image. As a principle, for the brightest image, the size of the exit pupil should be equal to the fully dilated iris of the human eye. The size of the fully dilated iris human eye is 7 mm. Though, it registers a decrease with the aging.
Exit pupil size is measured in mm and calculated by dividing the diameter of the objective lenses by the magnification number.
v. Eye relief
This is the maximum distance your eyes can be away from the binocular’s eyepiece lens and still get the full viewing angle. This particularly important for people who wears glasses as the glasses will hold the eyes back from the eyepiece.
Normal binocular have eye relief ranges from 5mm to 23mm, however if you wear glasses, it is generally recommended to get a binocular with eye relief of at least 14mm.
vi. Lens coatings
When you are checking out a pair of binocular, you might notices that there are indication on the type of coating used on the binocular – these coating are anti-reflection coatings applied onto the binocular glass surfaces to assist in light transmission.
Common symbols used are as follows:
- (MC), multi-coated; one or more surfaces are multi-layer coated
- (FC), fully coated; where all air-to-glass surface are coated. However do note that if any plastic lens are used, they might not be coated.
- (C), coated optics; where one or more surfaces are coated
- (FMC), fully multi-coated; all air-to-glass surfaces are multi coated.
Usually the better coated a binocular, the better the image quality and the higher the price as well.
4. Types of binoculars
Depending on the types of activity that you are using the binocular for, there are several types of binoculars in the market that you can look out for.
i. General Binoculars
General binoculars are used for the activities like hiking, watching sports or other outdoor activities. This includes opera glasses as well. If you want to engage in the outdoor activities, the compact and wide binoculars are desirable. You can keep them in the pockets or hang around the neck. Compact binoculars are generally from 7 x to 10 x magnification range.
ii. Hunting Binoculars
These binoculars are used for spotting prays that not visible to naked eyes. For this, 7x – 10x binoculars are preferred. But for the even longer range shootings, the binoculars with 12x – 16x magnification are considered the best. It should be noted that if you want to observe in the standing, a tripod should be used for a stabilizing effect. It decreases the shakiness of the hands occurred during standing. The larger magnification of the binoculars results in exaggerated shaking.
iii. Bird Watching binoculars
If you love the natural wilderness and have a passion for bird watching, binoculars are inevitable. The most standard binocular for the bird watching is 8 x 42. The 10 x magnifying or 12x magnifying binoculars are used preferably with 42 or 50 mm objective lens. The other desirable qualities that need to be considered while buying the bird watching binoculars are eye relief and close focus.
iv. Boating or Marine binoculars
For boating or marine activities, the high magnification binoculars are not recommended as the boats tends to be shaky which will cause the image to be more unstable. Hence, the most preferred one by the mariners is with 7x magnifications with 42 or 50 mm objectives. Sometimes, the 8x or 10x binoculars are also used by some mariners. Since you are in an environment surrounded by water, the waterproof feature along with the larger objective lens and rubber armoring should be top most priorities in this regard.
v. Concert or Opera binoculars
Also known as opera glasses or theatre binoculars are commonly used for the viewing and enjoying an opera or any show in the concert hall. They are generally made using Galilean optics and have magnification lower than 5x.
vi. Military binoculars
The binoculars are specially designed for the military purposes. The handheld ones are with 4x to 7x, but the prisms set used here are very large. The eyepieces have considerable eye relief. The rationale behind such combination is to prevent the darkening of the image during the shaking of the binoculars relative to the observer’s eye. The high specs models with large magnification and large objectives are used in the mounted form of course.
*Do note that the military range binoculars are controlled items in Singapore.
vii. Astronomical binoculars
For the astronomical purposes, the binoculars are designed with large objectives. It is to facilitate and increase
the gathering of the amount of the light. The higher the amount of the light, the easier it will be to observe the faintest stars.
viii. Night Vision binoculars
Generally these binoculars gives users the ability to see images in different level of light approaching complete darkness.
These binoculars are usually classified under gen 0, gen 1, gen 2, or gen 3 where the main difference is the type of light intensifier tube being used and the image quality (being gen 3 offering the highest quality)
*Please note that in Singapore, night binoculars that are are controlled items and only individual/companies with the proper permits are allowed to purchase to sell. Feel free to contact us to find out more.
Binoculars have very diverse uses – they can be used anywhere, from outdoor to indoors, daytime and night time. The kind of environment they are used decides some of their other features such as the waterproof or fog proof. If you are going to shop for the binoculars for any specific activity, choose the one that best suits your needs and has specifications as per demand of the activity.
And if after reading this and you still finds it hard to decide which model of binoculars to select, feel free to send us an email @ firstname.lastname@example.org and we will do our best to assist.
*P.s. If you have managed to read the guide all the way till here, we are very grateful for your time and attention and hopes that you find this guide helpful. In the above guide, we have tried our very best to research and provide as accurate information as we possibly could but we know that we are not perfect, and in the event that you should find any of the information incorrect or need further clarification, please feel free to let us know in the comment section.
Thanks for reading 🙂