Binocular Guide - Image Brightness

On any binocular there are two number. The first of these numbers indicates the magnification of the binocular, the last number is the diameter of the front lens (objective lens) measured in millimetres.

Therefore, an 8x40 binocular has a 40mm objective lens, similarly, a 10x50 binocular has a 50mm objective lens.

The size of the objective lens is one of the most important factors that affects how your binoculars work in different light conditions. The larger the objective lens;, the more light can get into the binoculars and you will get a brighter image. This means that for the same magnification, binoculars with 40mm objective lenses will have a brighter image than if objective lenses were 21mm. The problem is that binoculars with large objective lenses are large and heavy and also tend to be more expensive.

There are other factors that can affect the brightness of the image. One is magnification. There is a complicated law of physics behind this, but the outcome is that as the magnification increases, the brightness of the image decreases quickly. Another factor is the quality of the lenses, prisms and coatings in the binocular. Better quality glass and coatings give a brighter image (but cost more).

Generally, more expensive binoculars will be better quality. They are made with higher quality materials to a more exacting standard. This means that they produce clearer, sharper, brighter images.

One cautionary note: As with anything that you buy, the brand name on the product can add to the price of that product. Just because the prices on this website are less than some others, it does not mean that the binoculars do not offer images of at least the same quality.