🔭 Binocular Optics & FOV Lab

Optical performance evaluator for birdwatchers. Calculates exit pupil, twilight factor, relative brightness, and converts field of view across feet, meters, and angular degrees.

8.0° • 140 m/1000m
EXIT PUPIL
5.25 mm
Ideal for Twilight
TWILIGHT FACTOR
18.33
Detail in Low Light
BRIGHTNESS (RBI)
27.6
Geometrical Index
🦅 Field Birding Recommendations:
Eyeglass Wearer Tip: If you bird with eyeglasses or polarized sunglasses, look for an eye relief of at least 15mm to 18mm with twist-up eyecups twisted fully down to see the complete field of view without black vignetting rings.