I might be a little loose here, but I believe many rangefinders distance is based on reflection value. My Nikon 800 (800 yards) is good for about 400 yards which just about matches my long range ability.
I am tired of carrying to many items in the field and if pushed I would leave my rangefinder behind instead of my binoculars. The 6X glass in my rangefinder does not come close to replacing my 10X Leupold binoculars deer hunting. I spend a lot of time glassing.
Recently this item has captured my attention; it resolves the need for binoculars and a rangefinder.
http://www.bushnell.com/products/binoculars/fusion/FUSION® 1600 ARC
Binocular/Rangefinder
Binocular Features
• BaK-4 prisms with PC-3® phase corrective coating for superior resolution and clarity
• RainGuard® HD water repellent lens coating
• 100% waterproof
• VDTTM (Vivid Display Technology) - enhances display readout in all lighting conditions
• Carrying case, battery and neck strap included
Rangefinder Features
• 10-1600 yards ranging performance
• ARC (Angle Range Compensation) from -90° to +90°
• Bow Mode - provides line-of-sight, angle, and true horizontal distance from 10-99 yards/meters
• Rifle Mode - provides line-of-sight, angle, and bullet drop/holdover up to 199 inches
• VSI (Variable Sight-In) - allows sight-in distance options of 100, 150, 200, or 300 yards sight-in distance when in RIFLE mode
• Selective Targeting System - Automatic SCAN, BullsEye & Brush modes
• +/- one yard accuracy