The first digit in the type designation indicates the magnification factor. With 10x56 binoculars, the observed object appears 10 × larger than with the naked eye. To put it into simpler terms, the distance to the object shrinks by the magnification factor, i.e. a deer 400 m away looks like it is only 40 m away when you look through 10× binoculars.
- The object appears e.g. 10 x larger
- The distance appears e.g. 10 x smaller. The object appears 40 m instead of 400 meters.
For anyone interested in precise mathematical descriptions: the magnification is defined as the ratio between the tangent of the angle at which the height of the object appears with binoculars, to the tangent of the angle at which the height of the object appears without binoculars (see the diagram above). In other words:
Typical binoculars for free-hand observation feature 7x or 8x to 10x magnification. Higher magnifications deliver a larger image and, in theory, better detail recognition, but this benefit quickly becomes the opposite due to the effect of hand tremor increasing significantly. This is something that everyone should test themselves. When in doubt, a lower magnification is more enjoyable and the better choice in the long run. Apart from a steadier image, lower magnifications (e.g. 8 x 42 compared to 10 x 42) also offers additional benefits:
- The field of view is larger and you have a better overview of the surroundings.
- The exit pupil is larger, resulting in a brighter image at dawn.
- The depth of field, i.e. the area in the foreground and background that is still perceived as sharply focused, is also larger. You do not have to refocus for minor range changes constantly.