Leupold BX-4 Pro Guide HD Gen 2 (10x42) vs Vortex Viper HD 10x42

Field of view: Vortex leads

Vortex shows 341 ft at 1,000 yd on the Viper HD 10x42, which is 6.5 degrees. The Leupold BX-4 Pro Guide HD Gen 2 in 10x42 shows 314 ft, or 6 degrees.

Among the 87 models of this size with a field figure, the median is 336 ft. The Vortex sits above that median and lands at place 29 of 87. The Leupold sits under it and lands at place 70 of 87.

Eye relief and glasses: a tie

Both models print 17 mm of eye relief. The RSPB says eyeglass wearers should look for at least 16 mm, so both clear that bar. Audubon puts birding binoculars at 15 to 20 mm.

The median for 10x42 models is 16 mm, so both sit one step over the middle of their size. The eye spacing range is 56 to 74 mm on the Leupold and 55 to 74 mm on the Vortex.

Brightness at dusk: equal figures

The exit pupil works out to 4.2 mm on both models, calculated from 42 mm divided by 10. Nikon says a larger exit pupil gives a brighter view in dim light, and here neither one has an edge.

The calculated twilight factor is 20.5 and the calculated relative brightness is 17.6 for both. These come from the size alone, so they do not separate the pair. Coatings and glass quality are not scored by these figures.

Weight and close focus

The Vortex weighs 24.9 oz and the Leupold weighs 25 oz. The median for 10x42 models is 24.9 oz, so both sit close to the middle of their size and the gap between them is small.

Close focus is where they split. The Vortex focuses down to 6 ft and the Leupold to 9.3 ft. The size median is 6.6 ft, so only the Vortex is nearer than the middle. That helps with butterflies, insects and anything else close at hand.

Build and weather sealing

The makers describe the sealing in different terms. Leupold prints waterproof and fogproof for the BX-4 Pro Guide HD Gen 2. Vortex says the Viper HD is designed to withstand harsh weather and a wide range of temperatures, with argon as the fill gas.

Celestron defines waterproof binoculars as sealed and filled with dry inert gas, usually nitrogen. The Leupold uses the plain waterproof wording. The Vortex wording does not name a depth or a rating, so the two claims are not the same in print.

Price band, prism and use

Both models sit in the same maker list price band, $500 to $1,000. Both use a center focus wheel, both adapt to a tripod, and both name hunting as a use.

The Leupold is listed with a roof prism. Nikon says roof prisms benefit from a phase-correction coating to limit loss of resolution. For more hunting options, see binoculars for hunting, and for the wider field of choices see best binoculars compared.

BX-4 Pro Guide HD Gen 2 10x42 or Viper HD 10x42

Vortex takes two rounds with the Viper HD 10x42 on its figures: 341 ft of view and a 6 ft close focus. Everything else is level, from 17 mm of eye relief to the 4.2 mm exit pupil. The Leupold BX-4 Pro Guide HD Gen 2 in 10x42 gives you a clearly stated waterproof and fogproof build at 25 oz.