8x42 vs 10x42 Binoculars: What Changes on the Same Models

This guide compares the four binoculars we have on file in these two magnifications: the Vortex Diamondback HD in 8x42 and 10x42, and the Nikon Monarch M5 in 8x42 and 10x42. It's a comparison of these four models specifically, not of every 8x42 or 10x42 binocular. Because each brand offers both versions, you can see what changes when only the magnification changes. All figures are the manufacturers' published specifications.

What does 8x42 mean?

The two numbers describe a binocular's basic optics. The first number is the magnification: an 8x42 makes what you're looking at appear 8 times closer than with the naked eye, and a 10x42 makes it appear 10 times closer. The second number is the diameter of each objective lens, the large front lenses, in millimeters. All four binoculars in this guide have 42 mm objective lenses, so the comparison here is between 8x and 10x magnification.

Magnification

The 10x42s magnify 10x and the 8x42s magnify 8x, so the 10x versions make subjects appear 25% larger. All four have 42 mm objective lenses.

Field of view

Field of view is how wide an area you see at a given distance. On both brands, the 10x version shows a narrower area:

• Vortex Diamondback HD: 393 ft at 1,000 yards (8x42) vs 330 ft (10x42), about 16% narrower
• Nikon Monarch M5: 335 ft at 1,000 yards (8x42) vs 293 ft (10x42), about 12.5% narrower

Eye relief

Eye relief is the distance from the eyepiece at which you can see the full image. It's shorter on both 10x versions:

• Vortex Diamondback HD: 17.0 mm (8x42) vs 15.0 mm (10x42)
• Nikon Monarch M5: 19.5 mm (8x42) vs 18.4 mm (10x42)

Exit pupil

Exit pupil is the diameter of the beam of light leaving the eyepiece. Nikon publishes it for both versions: 5.3 mm (8x42) vs 4.2 mm (10x42). Vortex doesn't list exit pupil on its product pages, so we can't compare the Vortex pair on this.

What stays the same

• Close focus: unchanged within each brand. 5.0 ft for both Vortex models, 8.2 ft for both Nikon models.
• Weight: nearly unchanged. Vortex 21.8 oz (8x42) vs 21.3 oz (10x42); Nikon 22.2 oz (8x42) vs 22.6 oz (10x42).
• Weather sealing: all four are listed as waterproof and fogproof.

Price (MSRP) and warranty

• Vortex Diamondback HD 8x42: $319.99 MSRP
• Vortex Diamondback HD 10x42: no verified price on file
• Nikon Monarch M5 8x42 and 10x42: no verified price on file

The one price shown is a manufacturer's suggested retail price, not a live retailer price. Both Vortex models are covered by Vortex's VIP unconditional lifetime warranty. We don't have Nikon's warranty terms on file.

Which fits which priority

On these four models' specs: choose the 8x42 version if field of view or eye relief matters most, since it's wider and has longer eye relief on both brands. Choose the 10x42 version if magnification is the priority. Close focus and weight are not a reason to choose either, since they're the same or nearly the same within each brand.

Going deeper

• The 8x42s head to head: Vortex Diamondback HD 8x42 vs Nikon Monarch M5 8x42
• Product details: Vortex Diamondback HD 8x42, Vortex Diamondback HD 10x42, Nikon Monarch M5 8x42, Nikon Monarch M5 10x42
• Browse: Birding Optics

None of these binoculars has been field-tested here; this guide is built from manufacturer-published specifications and MSRP.