8x40 binoculars: 6 models compared

What 8x40 is used for

The first number is magnification and the second is the objective lens diameter in millimeters, according to the National Audubon Society. So 8x40 magnifies eight times through 40 mm lenses, and the exit pupil works out to 5 mm.

The Royal Astronomical Society names 8x40 as one of the two sizes usually recommended for starting out in astronomy. The British Astronomical Association calls 8x40s good and notes they are lighter than 10x50 or 7x50. ZEISS says an exit pupil of at least 4 mm suits dawn use, and 5 mm clears that figure.

For birding, Audubon says most birders prefer 7x or 8x power because the view is bright and wide. Celestron says a tripod is not required at 8x to 12x, so these binoculars suit hand holding.

How the 8x40 models differ

Field of view runs from 330 ft to 429 ft. Four models sit at the 429 ft median: the Pentax SP 8x40, Nikon Action EX 8x40 CF and the two Celestron models, the UpClose G2 and the Landscout. The Pentax SP 8x40 WP has the narrowest view at 330 ft.

The ZEISS Victory SFL 8x40 is the lightest at 22.6 oz, with 18 mm of eye relief and a 4.9 ft close focus. The median close focus for the size is 17.7 ft, so it focuses far nearer than its peers.

Eye relief has a median of 15.1 mm, and 3 of 6 models reach 16 mm or more, the least the RSPB advises for eyeglass wearers. The Pentax SP 8x40 WP leads at 20 mm, and the Nikon Action EX 8x40 CF gives 17.2 mm. Both Celestron models, listed under $100 by the maker, give 12 mm at 24 oz.

Porro prisms are the most common design here, and none of the 6 lists ED glass. The Pentax SP 8x40 WP weighs 31.7 oz, the heaviest of the group, against the 25.6 oz median.