Just as it is possible to choose different bodies for your spotting scope, so too can you choose different eyepieces. These eyepieces are available in a variety of magnifications, with either a fixed power or a zoom range. You can also choose an eyepiece that has a regular lens or a wide angle lens.
Perhaps you have been using the standard zoom lens on your spotting scope for some time and are looking to add another viewing option and experience more variety in your birding.
The advantage of adding a wide angle lens is that the spotting scope then has a wider field of view. The main benefit of a wider field of view is that it is easier to spot birds in the first place.
In this respect, having a wide angle lens on your spotting scope seems like a no-brainer. But are there any drawbacks to them? Do they work in combination with any size of spotting scope? What is the impact of a different diameter of objective lens?
Here we consider how the wide angle lens differs from a regular eyepiece on a scope.
Wide angle broadens field of view
Typically as magnification increases, so field of view decreases. So a narrower width of the landscape is visible at greater magnifications.
The benefit of a wide angle lens is that the field of view retains width even at higher magnifications. So while a wide angle eyepiece is listed as having a higher magnification on the spec, it will still have a similar field of view to a less powerful magnification on a regular lens.
In practical terms, on a wide-angle eyepiece, you might see magnification numbers at the lower end of the zoom range such as 25x. But this eyepiece would offer an equivalent field of view to a regular lower-magnification lens such as 20x.
This is a benefit because as well as getting a better close-up view with the extra magnification strength, there is no compromise in field of view. Zooming in does not decrease the field of view.
A wider field of view helps you to scan the landscape more efficiently as you can see more in one go. It helps you find birds more quickly.
The wider field of view also requires less movement of the spotting scope to pan across the scene. This in turn contributes a steadier image.
Wide angle = increased depth of field
With an improvement in the depth of field offered by a wide angle eyepiece, there can be less need to refocus. When switching from viewing one bird to another located further away, it can be necessary to change the focus to accommodate the change in distance.
Because the wide angle eyepiece tends to be more generous in the depth of field, then you can get away with refocusing less frequently. This is not only more convenient and requires less effort, but it also means quicker and more flexible viewing.
Wide angle lenses may be less tiring
For extended sessions of birding, a wide angle lens can offer relief to your eyes. The wide angle eyepiece may let your eyes stay more relaxed for a longer period.
Viewing with only one eye is more tiring than using both eyes, so there is a risk of eye fatigue or strain. Some people find that the use of a wide angle lens is easier on the eye muscles than a regular eyepiece.
Wide angle lenses can offer less eye relief
It can be more challenging to find a wide angle eyepiece that also offers long eye relief. Eye relief is of special importance to glasses wearers.
Shortened eye relief makes the spotting scope less forgiving to any kind of birder. This is because the positioning of your eye has to be really exact. It is crucial for your eye to be placed in close proximity to the eyepiece.
What combinations of wide angle eyepieces are best for birding?
For general birding
A wide angled 20x or 22x eyepiece works well with a 60mm scope.
Supplementary option
A 30x or 40x eyepiece is a good addition to the 20x all-purpose eyepiece.
For low light
A wide angle 20x or 30x combines effectively with a large scope, up to say 80mm. This could be either a fixed magnification or a high-quality zoom.
This larger scope also works well if much of your birding is done from a fixed position, in a hide, for instance.
For long eye relief or digiscoping
A wide angle 27x with long eye relief is best for glasses wearers. Extra eye relief is also more forgiving for digiscoping. (Potentially in the zoom option if the scope is of sufficient size and quality.)
For sea bird watching or raptor watching
30x or 50x wide angle eyepieces are popular choices for these purposes.
Final thoughts on wide angle eyepieces
For any purchase, and especially of expensive optics, it is important to be sure to take into account all the connotations of using a wide-angle lens, before spending any hard-earned cash.
This article is aimed at helping you check if a wide angle eyepiece suits your purposes for bird watching. On balance, how well will the wide angled eyepiece fit with any equipment or birding experience that you might already have accumulated?
There are so many options to consider when it comes to choosing eyepieces for scopes. Have you also thought about this question: Should I get a fixed or zoom eyepiece for my spotting scope?
With the increased field of view offered by the typical wide angle lens, this is a valuable upgrade to many birders’ equipment. With the ability to acquire bird targets better due to the wider view, hopefully an investment in a wide angle eyepiece would pay dividends in enjoyment and satisfaction for many years to come.