The Binocular Sky



There is a potentially bewildering array of letters that manufacturers use to give further information about binoculars in addition to the magnification and aperture. There is not an industry-wide standard of these, but here are most of the ones in recent and current use:

A: Armoured, usually with rubber (see GA, below).
AG: Silver coating on reflective surfaces of roof prisms (from argentum, the Latin for silver, whose chemical symbol is similar: Ag)
B: Depends on context and/or source of binoculars.
(a) Usual American, Chinese and Japanese usage. A Porro-prism binocular with each optical tube of one-piece construction (Bausch & Lomb or American style)
(b) Usual European usage: Long eye relief, suitable for spectacle-wearers (from brille, the German for spectacles).
C: Depends on context.
(a) Compact binocular (usually a small roof-prism binocular).
(b) Coated optics.
CF: Centre focus. Usually combined with another letter, e.g. BCF: Bausch & Lomb style centre focus.
D: Roof prism binocular (from dach, the German for roof).
F: Flat-field technology.
FC: Fully Coated optics.
FL: Fluorite lenses.
FMC: Fully Multi-coated optics.
GA: Rubber Armoured (from gummi, the German for rubber).
H: H-body roof prism binocular.
IF: individual focusing eyepieces. Usually combined with another letter, e.g. ZIF: Zeiss style individual focus.
IS: Image stabilised.
MC: Multi-coated optics.
MCF: Mini Centre-focus ("delta" Porro-prism binoculars, with the objectives closer together than the eyepieces).
N: Nitrogen-filled.
P or PC: Phase-corrected prism coatings (on roof-prisms)
P*: Proprietary (to Zeiss) phase coatings
SMC: Fully Multi-coated optics.
T*: Proprietary (to Zeiss) anti-reflective coatings.
W, WA, or WW: Wide angle.
WP: Waterproof.
Z: Porro-prism binocular with each optical tube of two-piece construction, with the objective tube screwing into the prism housing (Zeiss or European style).