Athlon Midas G2 UHD 10x42 vs Vortex Viper HD 10x42

Field of view: a tie

Both binoculars print a field of view of 341 ft at 1,000 yd, which is 6.5 degrees. Neither one leads, so you see the same width of scene through either pair.

Among the 87 models of this size, the median field is 336 ft. For field of view, Vortex holds place 29 and Athlon place 31, so both land a little above the middle. To see how that width plays out in use, try the field of view tool.

Brightness at dusk: equal on paper

Both models work out to an exit pupil of 4.2 mm, a twilight factor of 20.5 and a relative brightness of 17.6. These are calculated from the 10x42 size, not printed by the makers, so they cannot separate the two.

Nikon defines exit pupil as the objective diameter divided by magnification, and says a larger one gives a brighter view in dim light. With the same 4.2 mm on both sides, any difference at dusk would come from glass and coatings, which the figures here do not measure. The exit pupil tool shows the same sum for other sizes.

Eye relief: Viper HD leads

Vortex prints 17 mm of eye relief and Athlon prints 15.2 mm. The median for the size is 16 mm, so the Vortex sits above it and the Athlon below it.

The RSPB says eyeglass wearers should look for at least 16 mm. Only the Vortex clears that mark. Audubon puts the range for birders' binoculars at 15 to 20 mm, and the Athlon sits inside that range, so it still suits a bare eye. Glasses wearers can compare more pairs on the binoculars for glasses wearers list.

Close focus: Viper HD leads

Close focus is 6 ft on the Vortex. The Athlon stops at 8.2 ft. The size median is 6.6 ft, so the Vortex beats it and the Athlon falls short of it.

If you watch butterflies, dragonflies or a feeder a few steps away, the shorter figure lets you keep them sharp at a closer range. For distant targets the gap matters little.

Weight and handling: Midas G2 UHD leads

At 23.3 oz the Athlon is the lighter pair, and the Vortex comes in at 24.9 oz. The median for 10x42 is 24.9 oz, so the Athlon is under it and the Vortex sits right on it.

Both use argon gas for fog protection, and both are built for wet weather. Vortex adds center focus and is tripod adaptable, which helps on long sessions. Athlon uses roof prisms and ED glass, and its eye spacing runs from 57 to 74 mm against 55 to 74 mm for Vortex.

Price band and maker uses

Athlon lists the Midas in the $200 to $500 band, while Vortex lists the Viper HD in the $500 to $1,000 band.

Athlon names hunting, general use and birding as uses. Vortex names hunting. Compare more models in the same bands on the binoculars at $200 to $500 list and the binoculars at $500 to $1,000 list.

Midas G2 UHD 10x42 or Viper HD 10x42

Field of view, exit pupil and calculated brightness tie. Eye relief at 17 mm and close focus at 6 ft go to the Viper HD, while weight at 23.3 oz and the lower price band go to the Midas G2 UHD.