Given as the first number in a binocular description (e.g. 7x35, 8x50), magnification is the ratio of the focal length of the objective divided by the focal length of the eyepiece. This gives the magnifying power of binoculars (sometimes expressed as "diameters"). A magnification factor of 7, for example, produces an image 7 times larger than the original seen from that distance. The desirable amount of magnification depends upon the intended application, and in most binoculars is a permanent, non-adjustable feature of the device (zoom binoculars are the exception). Hand-held binoculars typically have magnifications ranging from 7x to 10x, so they will be less susceptible to the effects of shaking hands. A larger magnification leads to a smaller field of view and may require a tripod for image stability. Some specialized binoculars for astronomy or military use have magnifications ranging from 15x to 25x.
Kowa have also added a material to the outer lens surfaces that protects them from dirt and dust and also makes it easier to remove the inevitable fingerprints form the glass. This is important because the easier it is to clean a lens, the far less chance you have of damaging them when doing so. Note coatings like these are only commonly found on mid to high end optics, so to see them here is impressive and a sure sign that Kowa have paid particular attention to designing a very child friendly instrument.
Basic size (e.g. 8x30). As mentioned earlier, examples are sometimes seen where product physical dimensions or some other arbitrary figures are stated instead of magnification and objective lens diameter. This is very misleading and does not properly describe the product. Examples seen include a “40x60” in a compact monocular, where the objective lens diameter was actually 40mm (and the magnification was certainly not 40x). Another, described as "35x95", was actually a 20x40. Also, in a few cases, the overall diameter of the case surrounding the objective lens is used, rather than the lens itself, thus making it seem the objective lens is bigger than it truly is. Magnifications can also be exaggerated, an example of a claimed 16x in reality being closer to an 8x, with the number "16" probably referring to the eyepiece lens diameter. In this case, the claimed "16x52" was in reality an "8x42". Care is needed with such misleading and exaggerated specifications, more likely to be found on some very low budget items.
Weight is an important consideration when choosing a pair of night vision binoculars. Due to the sophisticated technology on the inside, nighttime binoculars tend to be heavier than regular ones. More advanced generations tend to be lighter but more capable than earlier generations. The ideal pair is not only well built to serve the purpose and last, but it is also lightweight for ease and comfort carrying it and using it on the move.
Binoculars usually have two set of numbers printed on them. These are magnification, and the size of the objective lenses used. For example, an 8x20 model makes subjects look 8x bigger while the diameter of its objective lenses is 20mm. Bigger lenses capture more light and are better in low-light conditions. For improved visibility at night, consider a pair of night vision binoculars.