How To Choose Binoculars For Bird Watching
Choosing the right pair of binoculars for bird watching can sometimes be a little tricky. Unlike camera lenses which for the most part are either effective or ineffective for majority of users, binoculars are far more relative to the person using them. A mistake many new birders make is looking at a list of binoculars and simply buying the highest rated pair, without consideration to whether they are the best binoculars for them, or whether they will cater towards the manner in which they are going to be used. Because of this, it is imperative to understand how binoculars work and which are the right type for you when it comes to bird watching.
Understanding Binocular Numbers
Binoculars have numbers attached to them, and you’ve most likely seen them before. The format used is NUMxNUM (Example: 7×40). These two digits provide information pertaining to both the strength and brightness of the binoculars. The first number tells us the magnification of the binoculars, in this case the binoculars have a magnification of 7 times. The number at the end tells us the diameter of the objective lens (the main lens), in this case it is 40mm.
Binocular Magnification: As discussed above, the first digit represents the zoom magnification of the binoculars. This means that the object you’re looking at will appear closer by that a multiplier of that number. A bird sitting on a branch 70 meters away would thus appear as though it was sitting 10 meters away when using the theoretical 7×40 pair. There are also binoculars that are known as zoom binoculars, these pairs offer an adjustable magnification, allowing the user to move between their focal distance.
Lens Diameter: The lens diameter is similar to how aperture works in photography. With a camera, the wider open your aperture blades are, the more light is let into your picture and the brighter your image. The same principle applies for binoculars when it comes to lens diameter. The size of the objective lens determines how much light will enter into your image, with larger values bringing you more light and lower values (smaller primary lenses) bringing in less light.
Exit Pupil: Image brightness isn’t solely dictated by the objective lens size, instead it is a combination of the objective lens size and the zoom magnification. A simple division on the values will provide you with your exit pupil value. You divide your objective lens size with the magnification amount to get the value. In this case, we would divided 40 by 7 to receive an exit pupil value of 5.7
Exit Pupil Values:
0 – 2 = Low (Suitable for use only in bright sunlight)
2 – 4 = Moderate (Suitable for sunlight or cloudy conditions)
4 – 6 = High (Suitable for the above, including dusk and dawn lighting)
7 – 10 = Very High (Suitable for night time use)
Eye relief is not of too much importance for the non-glasses wearing birder, however if you wear glasses, it becomes an extremely important aspect of your bins. Those who wear glasses should ensure that they get at least 15mm of eye relief on their bins. With a higher eye relief number generally being better, ideally one should aim for about 16 to 18mm of eye relief, as a glasses wearer. This measurement, and the concept behind eye relief is related to the distance between your eye and the glass of the binoculars. Image quality is reduced in cases of excessive eye relief and insufficient eye relief. The latter generally being the case of glasses wearers, while the former is often related to non-glasses wearing individuals using binoculars with the eye relief set too high.
One is able to adjust the eye relief as needed on most binoculars. This allows the individual to find the correct eye relief for themselves, ensuring a quality image. Below is an illustration which may help you recognize if you have the correct eye relief set on your bins. Individuals who have it set too high, may see an eclipsing of the image from the side, while those with an eye relief that is too low, will see strong vignetting around their view.
Bigger Isn’t Always Better
Having read the above, you may be thinking to yourself “Well more magnification is better, and who wouldn’t want more light in their image. I can’t go wrong with a pair of 15×70.”
The reality is that there is a price to pay for both larger objective lenses and for higher magnification. When considering buying binoculars for bird watching, you’ll want to make sure that you find the sweet spot and a pair that has values that cater to your situation. For example, a pair of 15x70s may offer enough light and a great amount of zoom. However be very careful about using any pair of binoculars with a greater zoom magnification than 10. The stronger the zoom, the more sensitive to your movement, this means that you will struggle with keeping your images steady.
A larger objective lens also means the binocular will be larger, and in many cases heavier.
The best binoculars for birding for most people, are binoculars that are between 8 and 12 magnification and with an objective lens of at least 40. The choice of whether to go with an 8, 10 or 12 is mostly personal preference, with each having its own pros and cons. However, most birders would suggest between 8 and 10, with 12x often posing more difficulty in getting onto a bird, especially in particular situations such as during pelagics or in cases of forest birding. The Swarovski EL 8.5×42 offer an 8.5x magnification, with unrivaled quality, and is a favourite among bird watchers.
Field of View
An important aspect of binoculars are also the field of view. For birders it is imperative that you be able to easily scan for the bird and a field of view that is too narrow can mean that once you eventually locate the branch the bird was on, it’s flown away. The higher the magnification, the lower the field of view. So while you may decide to opt for a 15x zoom on your binoculars with the idea that you’ll use them with support assistance such as a tripod, just remember that your field of view will also be very narrow and could hinder your bird watching. Because of this, we would highly recommend venturing as far as a 12x magnification, at the utter most.
Field of view is measured in a few ways and can be a little confusing initially if not understood.
FoV is measured as feet @ 1000 yards or sometimes meters @ 1000 meters. What this means, is that at 1000 yards, x feet of the object is visible. Wider fields of view therefore, would have more feet visible at 1000 yards, while the opposite is true for bins with a lower FoV, and this is then called the linear field of view. The same principle is obviously true for meters @ 1000 meters. There is a little maths involved in calculating the apparently field of view (AFOV) from the FoV and angle of view values, which is often best done through one of the many online calculators.
The most important thing about FoV however, is understanding how the concept works, more so than knowing the maths behind getting all the numbers.
Lens Coating and Weather Resistance
If you’re buying a pair of binoculars, ensure that they are well sealed, offering both anti-fogging and weather resistance. Cheaper binoculars will often be easily penetrated by rain or dust. Weather resistant binoculars will ensure that your bins stay dry and safe from dust. Lens coating is another important factor when it comes to binoculars and can easily change the entire quality. Cheap budget binoculars will often lack the correct lens coating, which results in light reflection which causes your image to appear dark and lose detail. Quality lens coating will ensure your binoculars prevent this light reflection and ultimately provide you with better quality viewing.
Higher range binoculars such as the Swars listed a few paragraphs above also offer excellent anti-fogging mechanics and all the bells and whistles to be expected from one of the most respected brands in the industry.
Not all binoculars are created equal and just because a pair may have the right zoom and objective lens size, doesn’t mean that you’re going to get good quality. Buying a pair of binoculars should be seen as an investment, rather spend a bit more and sit with a product of high quality that will last you well and do its job, than skimping on the money but finding yourself with a pair of sub-par bins. Be sure to read the reviews of binoculars when purchasing online, you’re bound to find other birders giving input on how they found their pair.
For beginner bird watchers, if you’re on a tight budget you may consider a pair in the R4000 – R7000 range which can offer good quality bird watching at a more affordable price.
Pricing & Quality
As with most things in life, binoculars are often a case of getting what you pay for. However, there are exceptions where certain more affordable pairs of bins may offer better quality than one would expect at the price point. Binoculars, for many, are not cheap… High end pairs can exceed R30 000 and not be viable for those on a budget. Thankfully for under R5000 you can pick up some really high quality binoculars, as we covered in our previous article. The difference between binoculars in the R5000 range and those at the R30 000 range are primarily related to image quality, specifically how the bins handle in low light and reflection of light on the lenses.
Higher end optics do certainly come with added quality, however many do notice diminishing returns when it comes to image quality for price point. For example, the build quality and image quality you will find when moving between an R800 pair of binoculars to a R4500 pair, is significantly higher than you will get moving between a R5000 pair and a R30 000 pair. There are many budget options (under R5000) available that offer high quality weather resistance and anti-fogging, quality visuals and strong build quality. For these high quality budget bins, the primary changes seen when moving to the top of the range options, is related almost entirely to low light image quality and ultimate, lengthy reliability than spans over decades.
It would be hard to argue against the purchase of high end optics, if financially viable. But for those on a budget, you should feel at ease knowing that you can still pick up some excellent bins for a fraction of the cost.