How we compare binoculars

Where the figures come from

For each binocular we read the maker's own product page, specification sheet, catalog or manual, and record the figures exactly as printed.

A figure the maker does not print is left out; nothing is estimated. Where a maker prints a figure in only one unit system, the other is converted and the specification table shows both. Where two of a maker's documents disagree, both figures are kept.

What is calculated

Exit pupil is the objective diameter divided by the magnification. Twilight factor is the square root of magnification times objective diameter. Relative brightness is the exit pupil squared. These follow the formulas Nikon, Celestron and Swarovski Optik publish, and every page marks them as calculated.

Medians, ranges and counts on a page are worked out from the binoculars on that page.

How lists are chosen and ordered

Each list has a rule stated on its page, built on makers' figures: a size range, a minimum eye relief, a weight limit or a list price band. A binocular that meets the rule is eligible; one that does not is left off, whatever its reputation.

Lists show the most popular models first. Labels such as widest field of view or lightest go to the model whose printed figure earns them.

Prices

Price bands use the maker's own list price in US dollars, where the maker prints one. Makers that publish no list price have models without a band. Store prices change daily and are never printed.

What this method cannot tell you

No binocular was handled or looked through. Sharpness, color, glare control, focus feel and durability are not in a specification sheet, so the pages are silent on them. Use the figures to narrow the choice to the sizes and models that fit your eyes, your hands and your use, then look through the finalists if you can.