Choose by Pupil Diameter (Brightness)
The larger the pupil diameter, the brighter the image appears.
The pupil diameter is calculated by dividing the objective lens effective diameter by the magnification factor. The brightness of the binoculars is shown by the square of the pupil diameter.
As long as the binoculars pupil diameter is approximately the same as a human pupil in a bright location (approximately 2-3 mm), images will not appear dark during normal observation.
Pupil Diameter and Binoculars Brightness
If the binoculars pupil diameter is greater than or equal to a human pupil, the same brightness can be obtained with the naked eye. However, if the binoculars pupil diameter is less than a human pupil, the image will appear darker than the naked eye. Let’s check the optimal pupil diameter for the intended use.
Relation between the Binoculars and Human Pupil Diameter
The human pupil diameter changes size depending on the brightness. Normally, the human pupil diameter is about 2 to 3 mm during the day (bright light conditions) and about 7 mm at night (dim light conditions).
Binoculars and Pupil Diameter Ranking
The larger the effective diameter and the lower the magnification, the larger the pupil diameter is and the brighter images appear.