8x42 vs 10x42 binoculars for birdwatching
Which magnification to buy, with the same models compared in both sizes.
Last updated: October 2026
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How we choose: we have not tested these by hand. Picks come from makers' published specs, independent reviews and what UK birders actually carry. Every pick was checked on Amazon UK on 22 October 2026. Prices move, so check on the day.
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What the numbers mean
The first number is magnification. 8x makes a bird look eight times closer, 10x ten times. The second number is the width of each front lens in millimetres. Both have 42mm lenses, so they gather the same light.
Divide the lens by the magnification and you get the exit pupil, the beam of light that reaches your eye. 8x42 gives 5.25mm. 10x42 gives 4.2mm. In good light your pupil is smaller than both, so you will not see a difference. At dawn, dusk and in dark woodland, the 8x42 looks brighter.
8x42 vs 10x42 side by side
| 8x42 | 10x42 | |
|---|---|---|
| Magnification | 8 times | 10 times |
| Exit pupil | 5.25mm | 4.2mm |
| Field of view | Wider, often 120m to 135m | Narrower, often 100m to 115m |
| Shake | Less visible | More visible |
| Low light | Brighter at dusk | Dimmer at dusk |
| Eye relief | Usually longer | Usually shorter |
| Detail at range | Good | Better, if held steady |
| Best for | Woodland, gardens, hides, all-round | Estuaries, reservoirs, coast, moorland |
Same model, both sizes
Makers' published figures. Field of view is metres wide at 1,000m. Prices are Amazon UK on 22 October 2026. Going from 8x to 10x costs you 10% to 16% of the view and 1mm to 4.5mm of eye relief, for about the same money and weight.
| Model | Size | Field of view | Eye relief | Weight | Price |
|---|---|---|---|---|---|
| Nikon Monarch M5 | 8x42 | 112m | 19.5mm | 630g | Around £269 |
| Nikon Monarch M5 | 10x42 | 98m | 18.4mm | 640g | Around £279 |
| Vortex Diamondback HD | 8x42 | 131m | 17mm | 618g | Around £235 |
| Vortex Diamondback HD | 10x42 | 110m | 15mm | 604g | Around £239 |
| Nikon Prostaff P3 | 8x42 | 126m | 20.2mm | 575g | Around £160 |
| Nikon Prostaff P3 | 10x42 | 122m | 15.7mm | Similar | Around £165 |
Choose 8x42 if
- This is your first or only pair.
- You bird in woods, parks, gardens or from hides.
- You wear glasses. Eye relief is usually longer at 8x.
- You often bird at dawn or dusk, or in winter light.
- You want to follow birds in flight. The wider view keeps a Sparrowhawk or a flock of finches in frame.
Choose 10x42 if
- Most of your birding is open country: estuaries, reservoirs, coast, moorland.
- You want more detail on distant waders, gulls and ducks without carrying a scope.
- Your hands are steady, or you brace on a hide shelf, wall or fence.
- You already own an 8x and want a second pair for open country.
If you need more than 10x, do not buy 12x or 15x binoculars. Shake wipes out the gain. Use a scope on a tripod. See spotting scope vs binoculars.
Our picks in each size
Nikon Prostaff P3 8x42Best 8x42
Around £160The best value 8x42. 126m view, 20.2mm eye relief, 575g. A pair that does everything a first-time birder needs, with glasses or without.
Nikon Monarch M5 8x42
Around £269ED glass for sharper, cleaner colour. 19.5mm eye relief and 2.5m close focus. Sold by Amazon when we checked.
Vortex Diamondback HD 8x42
Around £235The widest view here at 131m and 1.5m close focus. Good for woodland and for insects. Strong warranty.
Vortex Diamondback HD 10x42Best 10x42
Around £239The best value 10x42. A 110m view is wide for a 10x, and 604g is light. Close focus is 1.5m. Eye relief drops to 15mm, so try it with glasses first.
Nikon Monarch M5 10x42
Around £279ED glass at 10x, where it matters more, because colour fringing on distant birds is easier to see. 18.4mm eye relief is long for a 10x. The 98m view is narrow.
Want more choice? See the full binoculars guide, binoculars under £100 or binoculars for glasses wearers.
Frequently asked questions
Is 8x42 or 10x42 better for birdwatching?
8x42 is better for most UK birders. It has a wider field of view, a brighter image in low light and less visible shake. 10x42 is better for distant birds in open country, such as waders on an estuary.
Is 10x42 too much magnification for birding?
No, many birders use 10x42. It is the upper limit for handheld use. The view is narrower and shake is more visible, so it is harder for beginners and in woodland.
Which is better in low light, 8x42 or 10x42?
8x42. Its exit pupil is 5.25mm against 4.2mm for 10x42, so it delivers more light to your eye at dawn, dusk and in dark woodland.
Do 8x42 and 10x42 binoculars weigh the same?
Almost. The same model in both sizes usually weighs within 20g to 40g. The Vortex Diamondback HD is 618g at 8x42 and 604g at 10x42.
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