Many birding experts are hesitant to recommend zoom binoculars for bird watching. There is a perception that the quality of a pair of variable-magnification binoculars is not of an equal quality to a pair of binoculars with a fixed magnification.
This seems totally counter-intuitive. We will always find ourselves at different distances relative to the subject that we are attempting to view.
Surely it would be great to have bird watching binoculars where you can choose a suitable amount of zoom according to the particular situation that you are in?
It seems not. Let’s take a closer look at the reasons for the bird-watching experts’ aversion to zoom binoculars.
What are zoom binoculars?
The primary feature of zoom binoculars is their adjustable magnification. In the same way as a zoom camera lets you increase the magnification for a closer view of your subject, zoom binoculars allow you to zoom in or out to get more or less detail.
This feature differentiates them from traditional binoculars, which have a fixed magnification that cannot be changed. In contrast, zoom binoculars have the capability to be zoomed in or out, up to 20 times or more.
So you could begin viewing an object at a magnification power of 8x. From 8x, you could then zoom in to get a closer view to, say, 20x.
How can I identify zoom binoculars?
The specification for binoculars with fixed magnification will be listed with a pair of numbers, in this format: 8×42 or 10×50.
Variable or zoom binoculars will have three numbers. Of these three numbers, the first two – separated by a hyphen – indicate the range of magnification. This makes it easy to identify which binoculars have a variable magnification.
For example, 8-20×42, where the binoculars have a range of magnification from the lowest, 8x, to the highest, 20x. The 42 refers to the size of the objective lens – 42mm.
For more on the role and importance of the objective lens, please refer to this article on how to choose binoculars.
You may also see binocular specification with a slash in place of a hyphen. For example, 20/40×70.
Though these can be used with multiple magnifications, they are not technically zoom binoculars. This is because the eyepieces have to be switched over to alter the magnification.
How do zoom binoculars work?
Whereas a zoom lens on a camera works effectively with its one lens, the zoom on a pair of binoculars is more complicated because there are two sets of lenses.
Each tube of the binoculars is like a separate telescope. The pair of them should be synchronized in order for the viewer to be able to look through both at once for a clear view.
To get both of the sets of lenses at the same magnification at the same moment is a complicated problem for the manufacturers to solve. Their solution is to use a flexible band to connect the two zoom mechanisms together so that they work in synchronization.
The band needs to be flexible to allow the mechanism to move in and out. This necessary flexibility is also what can cause a slight fuzziness of the images because the left and right sets of lenses are never quite at completely the same magnification.
The moving parts, while enabling different distances of zoom, also made it very difficult to create a clear, crisp image.
Zoom binoculars: advantages and disadvantages
Pros of zoom binoculars
Different levels of magnification can be used, according to your location or situation. One pair of binoculars does the job, instead of needing to have multiple pairs of different magnification.
Flexibility at long range
The range of magnification means you can get a closer view without physically moving. If the object moves, instead of needing to change your position, you can just zoom in or zoom out to view birds with a higher or lower magnification.
This is especially useful for bird watching because your subjects can be fast-moving and unpredictable.
Different fields of view
Zoom binoculars have multiple fields of view because they have more than one magnification.
This helps when you are initially scanning the area, on the lookout for a bird, because you would like a lower magnification that offers a wider field of view. Once you have found your target, then you can zoom into the subject and use the higher magnification power to view in more detail.
It is also useful in instances when the area around the object is also of interest or where you cannot get physically closer to an object such as on raptor migration watches, from boats or at wetlands. For example, more than one bird can be viewed at the same time, by modifying the field of view.
The lower magnifications can capture a high standard of image quality, just like binoculars with fixed lenses.
The models available are priced affordably so that it is possible to try out this type of binoculars to see if it suits you.
Cons of zoom binoculars
A reduced field of view
Basically, the bigger the zoom, the narrower the field of view at the lower end of the binoculars’ magnification range.
The movable components inside the binoculars reduce the field of view by almost 50% in comparison to a fixed binocular of an equivalent magnification, so you could be losing around half of the field of view’s width.
The increased amount of optical elements inside zoom binoculars make them heavier than fixed magnification binoculars.
Depending on what magnification you want to use, you might effectively be carrying a larger instrument than you want to use at one time. Despite this, it can be possible to find a compact model of zoom binoculars, though they may cost more.
Image quality may suffer at higher magnification
The images can be fuzzy and of a lower quality than those of fixed magnification binoculars.
Reduced light transmission
In zoom binoculars, there are more optical components along the path that the light beams need to travel to reach the eye. As the light reflects off these components, along its path, some of it is lost.
The end result of this loss of light is reduced brightness in the image that the user sees. This makes zoom binoculars less sharp even in daylight, and even less effective in conditions where light is low.
Short eye relief
The distance of eye relief tends to be shortened by the zoom feature, making this kind of binoculars less suitable for people who wear glasses while they are bird watching.
Risk of unsteady images at higher magnifications
As with any binocular, an increase in magnification means a less steady image, due to natural hand shake.
While this is less noticeable with lower magnifications, when zooming in excess of 20x, you might need to invest in a tripod to stabilize the image.
Risk of collimation issues
It’s a challenge to achieve perfect synchronization between the two sets of lenses because they are moving parts.
This movement, even though it is very slight, means that the binoculars are not quite in perfect alignment, or collimated, as the zoom changes.
How should I choose zoom binoculars?
Perhaps now, having weighed up the benefits and drawbacks, you feel that zoom binoculars are a good option for you. If so, then how should you decide which model to buy?
What is your intended use?
How far from your subject do you anticipate watching from?
Is it more important to you to be able to see up close than seeing a perfect image?
Which power of magnification would best suit your anticipated viewing range?
For magnifications larger than 20x, we recommend using a tripod to minimize image shake.
Magnifications upwards of 10x will bring those birds mesmerizingly close for you. Plus it should still be possible to hand-hold your binoculars.
How portable will your binoculars need to be?
Perhaps you would like to take the binoculars on hiking trips or when needing to carry them some distance. In this case you need them to be weather-resistant and durable. Will you need to carry a tripod as well?
Is compactness important? The overall size of zoom binoculars tends to be larger.
If you do prefer to opt for a compact version, there may be some compromise in the quality of the image.
Is image quality the most important aspect for you?
In this case, the main specifications that affect the quality of the image are the magnification, the field of view and the objective lens size. Magnification will allow you to see the object more closely, but might suffer some resolution in the process.
Binoculars with a wider field of view are more user-friendly. A larger objective lens lets in more light. This gives a bright image especially in a dimmer environment or at time of day when the sun is low.
What is your budget?
A relatively low demand for this kind of binoculars has kept prices down.
Some bird watchers who would ideally like to have a choice of binoculars to suit different birding situations might see the option of being able to change magnification as a bonus, saving them buying two pairs of separate binoculars.
It is worth bearing in mind, though, that all of these requirements should be balanced out with the perception of some experts.
Zoom binoculars: limited choice of models on the market
There are not very many zoom binoculars on the market right now, in comparison to the very wide range of fixed magnification models available.
One variable-power example is the Leica Duovid. This product can be set on two different magnifications.
Few of the really top-end brands – Swarovski or Zeiss, for example – even produce zoom binoculars.
There are some very renowned brands, however, that do feature zoom binoculars in their line-up. Among these – with some featuring a Porro prism design – are Celestron, Nikon, Olympus, Pentax and Bushnell.
There is a pervasive opinion that the optical performance of zoom binoculars does not reach the same quality as a traditional fixed-magnification pair. With a low demand from consumers, there seems to be limited development in this area by manufacturers.
The complexity of the zoom binoculars’ optical components might also leave them more vulnerable to developing faults.
If the field of view is of less importance to you, then zoom binoculars might be worth a try, in instances where viewing is done in wide open spaces. When you are zoomed in, observation of the surrounding area is limited.
Viable alternatives to zoom binoculars
If the budget allows, having two separate pairs of fixed-magnification binoculars of different powers could add flexibility to your bird watching options.
There are also devices of 2x magnification, called doublers.
Doublers fix onto the eyepiece and – the clue is in the name – double the power of the binocular. Swarovski make these, as do Vortex.
Spotting scopes only have one single zoom mechanism so, unlike binoculars, they avoid the pitfalls of having to synchronize both sides of a pair.
A more compact alternative to a spotting scope with a variable zoom eye-piece, is a zoom monocular.
The benefit of the monocular is its smaller size and price. Being effectively only one half of a binocular, it is made up of only half the materials and therefore cheaper.
Are zoom binoculars best for the kind of bird watching you like?
With this overview of the benefits of zoom binoculars, balanced with an understanding of why bird watching experts have reservations about them, you will be better informed to see if they are a good option for you and the type of birding that you prefer.
- 1 What are zoom binoculars?
- 2 How do zoom binoculars work?
- 3 Zoom binoculars: advantages and disadvantages
- 4 How should I choose zoom binoculars?
- 5 Zoom binoculars: limited choice of models on the market
- 6 Viable alternatives to zoom binoculars
- 7 Are zoom binoculars best for the kind of bird watching you like?