How to choose a suitable lens for yourselfDecember 30, 2019
Excessive learning pressure and long-term use of electronic devices have made more and more people shortsighted, and glasses have become an indispensable part of most people’s lives. We wear glasses for a long time at our daily life, however, most people even do not know the basic knowledge of glasses. Some people only consider the beauty of glasses when they choose them, and ignore whether the lenses are suitable for them. So, today I want to introduce some information about glasses to you.
The common refractive index of lenses are 1.50, 1.56, 1.61, 1.67 and 1.74. The refractive index of the lens depends on the material that the lens used. In the case of the same thickness of the centre, if the lens has the same degree and material, the higher the refractive index , the thinner the edge of the lens. If the lens is made by the same company,different refractive index always means different material and prices. Usually, the lens with high refractive index is more expensive than the common one.However, we should know that the high refractive index is not always good for you, it also can make your eyes uncomfortable.
The Abbe Value is an important indicator to measure the clarity of the lens.And we can use the reciprocal of the dispersion coefficient to calculate the Abbe Value.The larger the Abbe Value is, the smaller the dispersion coefficient will be. On the contrary, the smaller the Abbe Value is, the larger the dispersion coefficient will be, and the worse the imaging clarity will be.At the same time, the refractive index of the lens will also influence the Abbe Value.The lens with high refractive index always has small Abbe Value.
The light transmission refers to the total amount of light that passes through the lens without being reflected and absorbed. The lens with high light transmittance can let us see things more clearly. Generally speaking, the light transmittance of the lens is also related to the refractive index. If you want to have a lens with high refractive index, maybe you need to suffer it is low number of the light transmittance. This is mainly because the surface of the lens with a high refractive index has a high reflection, which affects the clarity of the lens. However, after multilayer anti-reflection film is plated on the lens surface, it can counteract the reflection and improve the light transmittance. Therefore, when choosing lenses, we can not judge the transmittance only by refractive index.
There are still many things we need to consider if we want to choose a suitable lens for us, and here is only a small part of them. We may not have time to learn all the things about lenses, but when choosing glasses, please do not only consider whether they are beautiful, that is not a good habit.