In order to explore the spotting scope options thoroughly, we will discuss the different types of eyepieces that are available. This means weighing up the advantages and the disadvantages of the two categories of eyepiece that can attach to a spotting scope:
- fixed magnification
- variable magnification (also known as zoom or multi magnification)
Since you are wondering whether to get a fixed power or a variable/zoom spotting scope then it’s likely that you have already compared these types of optical instruments with others, like binoculars, for example.
One advantage that spotting scopes enjoy in comparison with binoculars is that their single optical path makes them more suited to zoom lenses. We discuss why this is in our article looking into the advantages and disadvantages of each here.
Binoculars vs spotting scope: which is better for birding?
While there is only a limited number of zoom binoculars on the market today, the range of spotting scopes equipped with this function is very wide. The differences between fixed and zoom scopes are more subtle than between fixed and zoom binoculars.
Let’s take a closer look at how they vary.
All about zoom magnification eyepieces on spotting scopes
Most popular combinations of zoom eyepieces start from 20x or 25x at the minimum, to 50x or 60x at the maximum. You will see the variable-zoom magnifications expressed like this: 20-40x, 20-60x, 25-50x.
So in conjunction with the size of the objective lens, the numbers are written like this: 15-45×60 and 20-60×80. Both of these are popular sizes of birding.
Zoom eyepieces are multipurpose
A zoom eyepiece increases versatility. But it is important to buy the best that you can afford for optimal light-gathering capabilities even at the higher magnifications.
The premium brands give images that are brighter, sharpest and with better contrast. In these cases, the representation of color is more true to life, increasing the chances of accurately identifying species whose details are subtle and not easily distinguishable.
Top-quality glass will also reduce instances of color fringing and distortion, maintaining a better image across more of its width.
Wider choice of zoom or variable spotting scopes
In your research so far, you may have noticed that there is a wider choice of zoom spotting scopes than fixed magnification scopes. The zoom capability is most popular among birders, mainly for the flexibility that it offers.
Variable or zoom eyepieces offer a range of magnifications and allow you to switch between different magnifications easily. Typically, a birder would locate birds initially using the smaller eyepiece, and then switch to the more powerful one when locked onto a bird that warrants a closer view.
Increased magnification risks more image shake
It’s likely that you will already be using a tripod in conjunction with your spotting scope. In order to maintain the steadiness of the image, it’s worth ensuring that the tripod is sturdy enough to accommodate any increase in shakiness when you increase the magnification to the upper range of your zoom.
All about fixed magnification eyepieces on spotting scopes
Some people prefer to stick with a fixed magnification eyepiece due to its wider field of view.
The fixed magnification eyepieces can also be brighter, due to their increased light transmission and the fewer glass components required. Because of this brightness, they are more suited to digiscoping.
The middle ground for many birders who prefer a fixed-power eyepiece seems to be the range of 20x to 30x magnification. This provides enough power to observe details close-up, without too much negative impact of reduction in field of view or of increased distortion. It is a good option for general purpose bird watching.
Wider field of view
The bonus of having a wider field of view is that it is more effective in scanning the landscape. As you are able to see more of the land at any one time, the task of actually finding the birds in the first place is easier. Using a wide angle eyepiece for this spotting stage of birding is even more advantageous.
Those in favor of zoom eyepieces, however, might argue that the difference between the field of view offered by each is negligible. For these birdwatchers, the fixed lens is not worth the compromise of only having one magnification, even if it seems to offer a somewhat more open view.
In addition, variable or zoom eyepieces are available as a wide angle version.
Is a wide angle lens better for a spotting scope?
Those in favour of zoom eyepieces might also argue that many birders use their spotting scope in conjunction with binoculars. So in this case there is less need to scan the landscape with the spotting scope as this has already been done with the binoculars – or with the naked eye.
If you envisage using mainly the lower power magnifications, such as 20x or 30x, with only very rare occasional use of, say, 60x, then it may be worth sticking with a fixed power eyepiece. Image quality tends to be superior with a fixed magnification at this range. Situations where this kind of magnification are applicable might be most commonly applicable include observation of waterfowl or raptor migration.
Budget considerations
Whether to use a fixed or a zoom spotting scope is a long-running debate. As technology updates and improves optics, the differences in quality between zooms and fixed eyepieces is lessening. Plus if premium level spotting scopes such as Swarovski or Zeiss fall within your budget, compromise in optical quality of a zoom eyepiece is less of a concern.
With a more constrained budget, a fixed power eyepiece at a lower price may offer better images than an equivalent zoom eyepiece. Quality zoom eyepieces are more difficult to manufacture. What you save on the fixed eyepiece compared to a zoom eyepiece (perhaps in the region of $100-150) may be better spent on a better quality of eyepiece, or even on upgrading the spotting scope itself.
Advantages and disadvantages of fixed eyepieces
Pros of fixed eyepieces for spotting scopes
- Wider field of view – easier to spot birds
- Wide angle lens increase field of view further
- Better light transmission = brighter image
- Eye relief tends to be longer – better for glasses wearers
- Lighter weight than zoom
- Lower chance of image distortion
- No adjustment needed – focus on viewing not zooming
Cons of fixed eyepieces for spotting scopes
- No flexibility – limited to one viewing option
- Less choice of models as not as widely manufactured
Advantages and disadvantages of zoom eyepieces
Pros of zoom eyepieces for spotting scopes
- Dual use – spot birds at lower magnification, zoom in for a closer view
- Versatility – opt for the most suitable magnification in each situation
- Field of view is not that much less than a fixed eyepiece
- Variety – keeps birding interesting with different views
Cons of zoom eyepieces for spotting scopes
- Narrower field of view makes it less easy to scan for birds
- The time it takes to switch power can mean missing out on a view
- Reduced light at higher magnifications impacts the brightness of the image
- Larger objective lens needed – so increased size and weight
- Reduced eye relief
- Can experience a tunnel effect
- Most costly – more components needed, plus it’s best to invest in a high-quality zoom to fully reap the rewards
- Sturdy tripod required to minimize movements and ensure steady images (adds weight and bulk)
- Thermal movements/mirages impact long-range views in warm weather
Final thoughts on fixed vs zoom spotting scopes
Whether a spotting scope is of fixed magnification or zoom magnification depends on which eyepiece is attached to the body of the scope.
A user can choose whether they prefer an eyepiece that is fixed magnification or offers a variable range according to the kind of birding that they like to do. We’ve explored the pros and cons of both sorts of lenses in relation to their common usage situations.
Fixed magnification eyepieces are valued for their increased brightness and wider field of view. They are generally considered more suitable for digiscoping.
Variable or zoom eyepieces are very popular for their overall usefulness and adaptability. Some zoom lenses lose a little in the field of view and sometimes there can be a compromise in brightness. But in many of the highest quality products this difference is minimal.
The real plus point for all birders, whether you opt for a fixed or a zoom spotting scope, is that there is such a great availability of amazing optical products to suit all requirements.