Choosing a Binocular for Birdwatching

It can be argued that a binocular is the one piece of absolutely essential kit for birdwatching.

A good binocular at the very least enhances the enjoyment of watching birds, allowing more detailed observations at distances less likely to disturb the birds from their natural behaviours.

The array of models and the wide range of prices can present a very difficult choice for someone looking to either purchase their first binocular or upgrade from an existing one.

When advising people, we very much put the customers needs first. Applying any criteria the customer flags up as important and trying to provide the best fit from there has been a successful formula.

What do the numbers mean?

The first number quoted is the magnification e.g. 8 or 10. 8 & 10 are the most common magnifications as they provide enough power to make out details at a reasonable distance whilst still being hand-holdable.

We are often asked if there is any complicated arithmetic in relation to magnification. The simple answer is no! The birds will appear either 8 or 10 times closer!

The second number commonly seen is the diameter of the objective lens (literally the lens nearest the object). The bigger this lens is in relation to the magnification, the brighter the image will be in duller light conditions.

For example an 8×42 binocular will be brighter than an 8×32. We have found an easy way to understand this is by relating it to the size of your own pupil in given light conditions.

Dividing the objective lens diameter by the magnification gives us the diameter of the exit pupil (literally the size of the hole the light is coming through to your eye). As our own pupils expand in lower light, we need a corresponding size of exit pupil to allow enough light into our eyes to resolve the greatest detail.

This is also determined by other factors such as the quality of the glass and coatings on the lenses which will be discussed below.

Hence the commonest specifications being 8×32, 8×42 and 10×42 as our own pupils will be less than 4 or 5mm in most daylight conditions – allowing enough light without resorting to a big, heavy, cumbersome and more expensive unit. (Other common specifications are 8×25 & 10×25 which, although letting in less light, are much more compact and lightweight if these are major considerations e.g. for walking or travel).

The other number most commonly quoted is the field of view, or width, of the resulting image.

This is, somewhat counterintuitively, determined largely by the magnification and NOT the diameter of the objective lens!

The higher the magnification, the narrower the field of view.

As field of view can be thought of as a sector (or slice of cake), it is relatively easy to find distant subjects as the view is opening out. Relatively close subjects can be harder to find with a narrower field as they are at the ‘thin end of the wedge’.

As a rule, a wider field of view is helpful rather than essential.

How to choose from such a wide range of prices?

The question ‘why do the prices vary so widely’ is answered by the fact that glass, coating, and build quality varies widely.

Our advice is to:

  1. Decide which specification is most suitable by trying 8x v 10x and feeling the weight to help narrow the choice.
  2. Once a specification is decided upon, we recommend trying a few within your budget to see if you can see any differences in the image quality, ease of use and general comfort.
  3. It is useful to compare models by looking at distant objects to determine the level of detail which can be resolved, looking against the light to see if contrast is good (a better binocular will allow some colour and detail to be discerned where a basic one may render birds as silhouettes).
  4. Check for colour fringing where there may be a wide band of colour around a bird, spherical aberration (noticeable curvature to straight lines), colour (cheaper binoculars may have a ‘warm’ cast or tinge to the image) and the overall ease on the eye. Does the image ‘snap’ into focus quickly – after all, wildlife doesn’t generally wait for us to organise ourselves!
  5. Is the binocular comfortable to hold?

Can you compare online?

Yes, our Compare tool on the website allows you to see your preferred choices side by side so you can compare prices, specifications and look of the binocular. To add your favourites to this tool, select the criss crossing arrow icon that is available on every product.

Spending a bit of time when choosing really helps to settle on the right instrument for the individual and a much more enjoyable field experience.