Choosing binoculars: what do 8x21 and 10x25 mean?

Autumn is one of the finest seasons to head outdoors with binoculars. Large flocks of birds migrate across the country, the woods change colour and there is plenty to see in the dunes and water meadows. But what do those numbers on binoculars actually mean, such as 8x21 or 10x25? And which pair suits you? In this article we explain it simply, with tips to get a sharp view straight away.

What do the numbers on binoculars mean?

Every pair of binoculars has two numbers, for example 8x21:

• The first number (8) is the magnification. A bird 80 metres away looks as large as if it were 10 metres away.
• The second number (21) is the diameter of the large front lenses (the objectives) in millimetres. The larger the lenses, the more light the binoculars gather.

Larger lenses give more light, but also make the binoculars bigger and heavier. Compact binoculars with small lenses, on the other hand, fit in your coat pocket.

8x or 10x magnification?

More magnification always sounds better, but it is not that simple. At higher magnification every movement of your hands is magnified too. The image then shakes more and you see a smaller part of the surroundings.

	8x magnification	10x magnification
Handheld image	Steadier	Shakes more
Detail at distance	Good	More detail
Following moving animals	Easier	Harder
Ideal for	Walking, holidays, concerts	Birds, landscapes, sports matches

Not sure? For most people 8x is the easiest place to start. If you mainly want to see detail far away and can hold the binoculars steady, 10x is a good choice.

Light gathering: viewing in daylight and at dusk

Divide the lens diameter by the magnification and you get the exit pupil: the diameter of the beam of light reaching your eye. For an 8x21 that is about 2.6 mm and for a 10x25 about 2.5 mm.

During the day your own pupil is small, so compact binoculars are more than enough for a bright image. At dusk your pupil opens up and binoculars with much larger lenses (such as 8x42) have an advantage. Compact binoculars are therefore mainly intended for daylight use, and there they are especially handy, because you always have them with you.

BAK4 prisms and FMC coating

Inside binoculars are prisms that turn the image the right way up. Prisms of BAK4 glass transmit more light than simpler glass (BK7), which keeps the image brighter towards the edges too.

FMC stands for fully multi-coated: all glass surfaces have several anti-reflective layers. That means less light is lost to reflections and you get a brighter image with more contrast. Both Travelhawk compact binoculars have BAK4 prisms and FMC lenses.

Which Travelhawk binoculars suit you?

• As light and small as possible: the Travelhawk Compact Binoculars 8x21 weigh about 165 grams and fit in your coat pocket. Ideal for walks, holidays, the city or a concert. The 8x magnification makes the image easy to hold steady.
• Further and more detail: the Travelhawk Compact Binoculars 10x25 magnify 10 times and have slightly larger lenses. A good choice for birdwatching, landscapes and sports matches.

Both pairs are splash-proof and dustproof and come with a neck cord and protective caps. See them both in the binoculars collection.

How to set up your binoculars properly

1. Eye spacing: fold the two halves of the binoculars towards or away from each other until you see one round image.
2. Focusing: close your right eye and turn the central wheel until the image is sharp for your left eye.
3. Dioptre: now close your left eye and use the dioptre adjustment (usually on the right eyepiece) to sharpen the image for your right eye. After that you only need the central wheel.

Tips for a steady, sharp image

• Keep your elbows against your body or lean on a tree, fence or wall.
• First find the animal with your eyes, then bring the binoculars up to your eyes without shifting your gaze.
• Wear the binoculars on the neck cord, so they are always within reach and cannot fall.
• Clean the lenses with a blower or soft brush and then a microfibre cloth, not with your jumper or a paper tissue.
• Never look at the sun through binoculars, not even briefly. That can cause permanent eye damage.

Binoculars for birdwatching

For birdwatching a magnification of 8x to 10x is ideal. That brings birds close without the image becoming too unsteady. Also look at:

• Field of view: the wider your view, the easier it is to follow a bird in flight or darting away.
• Weight and size: birdwatching often means long walks. Light, compact binoculars you can carry all day without noticing them.
• Weather resistance: splash-proof binoculars can handle a shower in the dunes or the woods.

Take your time: stand still, wait for the birds to show themselves and use a bird guide or app to identify them. Stay on the paths and keep your distance, so you do not disturb the animals.

Binoculars for children

With their own binoculars children head outdoors full of curiosity. For children, choose a light, compact pair such as the Travelhawk 8x21 of about 165 grams. With 8x magnification they hold the image steadier than with a stronger pair.

• Always have them wear the binoculars on the neck cord, then they will not drop or lose them.
• Help with setting the eye spacing: push the halves together until they see one round image.
• Explain that they must never look at the sun through the binoculars.
• Make a game of it: who is the first to spot a bird of prey, a squirrel or a deer?

Packing list for a nature walk

• Binoculars with neck cord
• Vacuum flask with hot tea or coffee
• Rain poncho for an unexpected shower
• Walking socks and sturdy shoes
• Compass if you go off the marked paths
• A headlamp, because it gets dark early in autumn

Frequently asked questions

What does 8x21 mean on binoculars?

The 8 is the magnification: you see everything 8 times closer. The 21 is the diameter of the front lenses in millimetres. The larger that number, the more light the binoculars gather.

Are 10x binoculars better than 8x?

Not necessarily. With 10x you see more detail, but the image shakes more and you see a smaller part of the surroundings. 8x is steadier handheld and easier for following moving animals.

Which binoculars are good for birdwatching?

For birdwatching in daylight, compact 8x or 10x binoculars are fine. Choose 8x if you want to follow birds in motion and 10x if you mainly want detail further away.

Can you use compact binoculars at dusk?

You can, but the image goes dark sooner. Compact binoculars are mainly made for daylight use. For dusk, binoculars with larger lenses are more suitable.

Which binoculars are suitable for children?

Light, compact binoculars with 8x magnification, such as the 8x21. They fit small hands well and give a steady image. With the neck cord they stay within reach.

Ready to head outdoors? Take a look at our binoculars and everything for walking. Free shipping from €40, 1-2 working days delivery and 30 days free returns.