What Does 10x42 Mean? And How to Set Up Your Binoculars Properly
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You've got your binoculars, and somewhere on them it says 10x42. But what does that actually mean? And why does the view sometimes feel blurry or tiring, even with a good pair? In this guide we explain the numbers and show you how to set up your binoculars in four simple steps. It takes about a minute, and it makes a big difference.
What does 10x42 mean?
10 = the magnification
The first number tells you how many times closer things appear. With 10x binoculars, a bird 100 metres away looks as if it's only 10 metres away.
More magnification isn't always better. The higher it goes:
- the more every tremble of your hands shows up in the image
- the smaller the area you see, so it's harder to find a bird and follow it
- the darker the image becomes
That's why most birders choose 8x or 10x. 8x gives a wider, steadier view, which is great in woodland and for birds on the move. 10x shows a bit more detail, which helps when you're watching open fields, lakes or the coast.
Good to know: image-stabilised binoculars. Do shaky hands bother you, or would you like more magnification without a wobbly view? There are also image-stabilised binoculars. Built-in sensors detect the small movements of your hands and the optics compensate for them, so the image stays steady! They are heavier and pricier than regular binoculars, and most need batteries. But for anyone with less steady hands, or for scanning distant birds over a lake or the sea, they can make a real difference!
42 = the size of the front lenses
The second number is the diameter of each front lens in millimetres. Bigger lenses let in more light, so the image stays bright early in the morning, in the evening or under a grey sky. The trade-off is that bigger lenses make binoculars heavier.
- 42 mm is the all-round choice for birding
- 25–32 mm is lighter and more compact, handy for travel, but darker in poor light
- 50 mm and up is very bright, but heavy to carry all day
10x42 in one sentence: the binoculars bring birds ten times closer, and their 42 mm lenses gather enough light for a bright view from dawn till dusk.
How to set up your binoculars, step by step
Step 1: Set the width
Hold your binoculars and look through them. Fold the two halves closer together or further apart until you see one round image instead of two overlapping circles. Everyone's eyes are a different distance apart, so this step is personal.
Step 2: Adjust the eyecups
The rubber eyecups twist or slide in and out.
- No glasses? Twist them all the way out.
- Wearing glasses? Twist them all the way in, so your eyes are close enough to see the whole image.
If you see a dark ring around the image, adjust them a little further.
Step 3: Set the diopter
This is the step most people skip, yet it's the most important one. Most people's eyes are slightly different, and the diopter corrects for that. Usually it's a ring near the right eyepiece, often marked with + and –.
- Pick something with fine detail, such as a sign or a branch, about 20–30 metres away.
- Close your right eye, or cover the right lens.
- Turn the centre focus wheel until the image is sharp for your left eye.
- Now close your left eye.
- Turn the diopter ring, not the centre wheel, until the image is sharp for your right eye.
Don't worry if it takes a few tries to get it right!
Done! Note where the diopter is set. You don't need to change it again unless someone else has used your binoculars.
Step 4: Focus
From now on, use only the centre focus wheel to switch between a bird nearby and one far away. Both eyes will be sharp at the same time.
Bonus tip: Find the bird with your eyes first, keep looking at it, and then bring your binoculars up to your eyes. That's much faster than searching through the binoculars.
Ready to go
Now that your binoculars are set up properly, birding will be sharper, more comfortable and a lot less tiring for your eyes.
Happy birding! And if you'd like a T-shirt that's as bird-nerdy as you are, take a look at our collections →