The objective lens size gives you an idea of the size of the binoculars and how much light they can gather.
For instance 10×42 means they have a magnification of 10 times and an objective lens size of 42mm. Phase coating/correction (n/a for porro prism shapes) = Corrective contrast, brightness and sharpness/resolution.Īnti-reflection lens coatings = Fully coated, multi coated or both.Ĭoated = A single anti-reflection coating on some lens elements = enables more light to be transmitted to you than if there was no coating.įully coated = A single anti-reflection coating on all air to glass surfaces = better than a single coating. These are usually made up of two numbers, separated by an x and they refer to the magnification and size of the binoculars. The numbers on binoculars tell you their strength (magnification) and their size (objective lens diameter). Such treatments and coatings require expertise and quality control which is why RSPB works with Viking to produce quality optics, and also sell well-known brands such as Swarovski and Leica.ĮD lens/glass (Extra low dispersion glass) = Reduces colour fringing which can increase clarity and brightness quicker focusing. Some are better than others so it's important to try out the binoculars in person rather than base your decision around these factors. There are various treatments for the glass lens to improve image quality.