How To Choose Binoculars For Butterfly Watching (Best UK Guide)

How To Choose Binoculars For Butterfly Watching (Best UK Guide)

If you love nature, and spend as much of your free time watching nature as you can, you’ll probably have encountered a problem that’s common among nature lovers. Every time you get close enough to a butterfly to get a really good look at it, it flies away. Our ancestors solved this problem by catching the butterflies and moths, and pinning them to a board.

Of course to achieve this they had to first kill the insect, then carefully extend its wings and pin it to their collecting table or wherever they displayed them. This is not only a bit cruel, but now (thankfully) against the law in the UK. Sadly not for all species, but many are protected under the Wildlife and Countryside Act 1981 [1].there are many organisations [2] that are doing conservation work to help protect the Great British wildlife, which is great, but we need to do our bit too.

Although if you read through this act, well at least the section on butterflies you’ll find a selection of species that are protected, We believe that all of nature should be covered and to that end, we would like to suggest a better way to get a close up view of butterflies, moths and other insects in their natural environment. That is to invest in a close focus pair of good quality binoculars.

What Is Close Focus?

Close focus binoculars have been described as long distance microscopes. The very best way to observe insects in their natural environment, without disturbing (or killing) them  is with a pair of close focus binoculars. 

Close focus is the closest distance that you can see clearly through the lens of the binoculars. In many cases, the close focus is around 3 to 6 foot (1 to 2 metres) which is like looking at your own feet in close detail through the lens of binoculars.

Magnification and objective lens size

Even if your primary objective is to watch butterflies, you’re going to need to find them first. For that we recommend a decent pair of binoculars with a close focus of 2 metres and a magnification of 8x and an objective lens diameter of 32mm. This allows you to see an object 8 times larger than it actually is, giving you plenty of scope to find the butterflies before sneaking up close enough to use the close focus.

Plus the 32mm diameter objective lens will allow plenty of light to illuminate your image when viewed through the binocular lens. So the numbers for magnification and the objective lens will read like this;


As you have probably already worked out, the 8x indicates 8 times magnification and the 32 is the size of the diameter of the objective lens (32mm). There are many 8×32 binoculars for sale, so you’ll need to check the specs to find out what the close focus is. 

What’s The Objective Lens?

The objective lens is the larger of the 2 lenses, and the one furthest from your eyes – closest to the object you’re looking at. The size of the objective lens is an important piece of information for a number of reasons.

  1. The objective lens diameter size determines how much light can enter the binoculars, which in turn shows how bright the image you’re looking at will be (very useful in low light conditions like dawn, dusk or even a cloudy day).
  2. The actual size of the binoculars are determined by the size of the objective lens – Compact binoculars have an objective lens diameter of less than 30mm
    Midsize binoculars have an objective lens size of between 30 to 40mm
    Full size binoculars have an objective lens size of more than 40mm.
  3. The objective lens size is in direct proportion to the weight of the binoculars. The higher the objective lens size the more the overall binoculars will weigh (this is due to the size and weight of the optical glass used to make the lens).

The Field Of View (FoV)

The field of view is how much width you can see through the binoculars from left to right whilst looking straight ahead. There is a direct relationship between magnification and the field of view – as the magnification increases, it lowers the field of view. This is pretty obvious if you think about it, as you zoom in closer to the object, you lose the view that surrounds the object.

To find out the field of view check the specs, it will be expressed in one of two ways,

  1. Angular
  2. Linear

The angular field of view is shown like this; 8° and anything between 6° and 8°is considered good in the world of binoculars.

The linear field of view is expressed in one of two ways, either as feet per thousand yards, or metres per thousand metres. Anything between 105 metres per 1,000 metres to 140 metres per 1,000 metres or 315 feet per 1,000 yards to 420 feet per 1,000 yards is considered good, which is the same as 6 to 8 degrees.

To convert the angular FoV to the linear 1° is equal to roughly 17.5 metres or 52.5 feet per 1,000 metres/yards. So Just multiply the angular by one of those two to get the linear FoV.

Which Binocular Type Is Best For Butterfly Watching?

There are two main types of binoculars which are Porro prisms and roof prisms. Without going into too much detail, porro prisms are the classic M shape (the shape is caused by the way the prisms are set at an angle to produce the magnified upright image). Porros are on the whole, larger, heavier, more bulky, harder to waterproof, easier to damage (optically, the offset prisms can easily get knocked out of alignment which leads to eyestrain, headaches, and migraines). On the plus side they are considerably cheaper than the equivalent roof prism.

Roof prisms have the prisms set in the roof of the lens tubes, they are smaller, lighter, more compact, easier to carry, easier to fully waterproof, easier to conceal or pack away in a backpack, but they can be relatively expensive compared to Porros.

For close focus butterfly viewing binoculars we would recommend roof prisms as there is far more choice for close focus binoculars in roof prisms than Porros.

Do Binoculars For Butterfly Watching Need Waterproofing?

This is a good question, because you’re not likely to see many butterflies when it’s raining. But as we can’t control the weather, it’s more than likely that you’ll get caught in a downpour at some time.  It’s always best to prepare for the worst so you should have waterproof binoculars. IPX6 will give you full protection from rain but IPX7 can be submerged in water, as we suspect you’re not planning on looking for butterflies under water, IPX6 will do you fine.

The IPX system is an industry coding system for waterproofing and it’s quite confusing so trust us on the IPX6 thing. If you are interested in learning about the industry waterproofing code there are many online companies that specialise in waterproofing one such company that makes waterproof cases has a good easy to follow diagram [3]

Fog Proofing

Not absolutely necessary, but worth having, fog proofing means your binocular lenses will not fog up due to temperature fluctuations. To achieve fog proof binoculars, they remove all of the air from the lens tubes, and replace it with either nitrogen or argon gas. Neither of these gasses contain moisture and so won’t fog up. Once the gasses are sealed in, no dust or microbial debris can enter, which means extra protection.

Protective Coating

Rubberised protective coatings are often added to binoculars to improve grip and to protect against bumps and scrapes. For exploring in nature it’s a good idea to go for rubber coated binoculars, you’re investing over £100.00 at least and probably nearer £250.00 so you’re not likely to want to get them scratched or dented.

Lens Coatings

Lens coatings are almost as confusing as waterproofing codes, there are just so many types of lens coatings available. Without bombarding you with long lists of useless information, the best coatings to go for are fully multi-coated lenses. This means every lens, inside and out has been fully coated in multiple coats to reduce glare, and improve the colours and brightness of the image.

Prism Types

The glass used to make the prisms makes all the difference. Top quality manufacturers use two types of glass prisms, which are BAK-4 and BK-7. They are both optical glass but BAK-4 has slightly less imperfections than BK7. The easiest way to tell which glass was used to make the prism is to turn the binoculars over, look through the large lens (objective) at arm’s length. If you see a perfect circle of light, they’re BAK-4, if the image has square edges, it’s BK7.

Just to reiterate the point, both are precision optical glass and both will produce great clear images. Having either type shows that the binoculars are made to an exceptionally high standard.

ED Glass

If the specs mention ED glass this means the glass used is Extra low Dispersion glass. Which in plain English means the image produced will be crisp, sharp and clear.

Interpupillary Distance (IPD)

This is the distance between the centre of your pupils. The usual distance is 64mm but there are some people with different IPDs so check the specs to see if the IPD suits you. Some are adjustable but you will need to check.

Eye Relief

This is the distance between your eye and the ocular (closest) lens whilst being able to see the full field of view. Common eye relief is anywhere between 13mm and 16mm which is fine for most of us. If you need to wear glasses constantly, you’ll need long eye relief. These are usually between 16 and 24mm, check the specifications for more details.

How Much Will Butterfly Watching Binoculars Weigh?

Binoculars aren’t that heavy nowadays, the 8×32 we recommended earlier weighs 0.521 kg (18oz) which is light enough to carry all day with no issues.


Using a harness will not only lessen the weight of the binoculars at your neck, but will also stop the binoculars from bouncing around. You can usually pick up a binocular harnesses from £10 to £30 which is quite cheap when you consider the benefits.

How Durable Are Binoculars For Watching Butterflies?

As we’re recommending roof prism binoculars for watching butterflies and other insects, they will take quite a lot of punishment. That’s not to say you can throw them around, but accidental bumps and scrapes won’t cause any damage other than cosmetic, and if you go for rubber coating they won’t even suffer that.

What Price Can You Expect To Pay For Butterfly Watching Binoculars?

Prices range from around £100.00 upwards to around £1600 depending on brand and model but for around £130.00 you could do worse than buying the Hawke Nature Trek 8×32 with a close focus of 2 metres BAK-4 roof prisms fully multi-coated optics, waterproof and fog proof. Includes a lifetime guarantee, and a field of view of 7.4° (388 feet per 1,000 yards/ 129 metres per 1,000 metres) and an eye relief of 18mm and twist up eyecups.

Frequently Asked Questions

What is close focus on binoculars?

Close focus is the distance between the binoculars and the object you’re looking at while still having a clear image. Lower magnification and smaller objective lens size tend to have better close focus.

How close can binoculars see?

Close focus binoculars have an average of 6 feet (2metres) viewing distance. This means you are able to clearly see objects as close as 6 foot with a clear image.

What is minimum focus distance for binoculars?

The minimum focus distance for binoculars averages at around 6 ft (2 metres).