In the market now, the color of coated lenses (HMC) are: green film, blue film, gold film, red film, light blue film, yellow-green film and other varieties, which one do you think is good for consumers? For the average consumer and the general staff of the dispensing store, it can be said that there are few can say understand. There are many different opinions, why? This can be explained from two aspects: 1, know but do not say for a class, in order to sell the interests, in order to get more profits, can only fool the consumer a little. 2, really do not know, no way to say. I now give a correct explanation: from the optical theory, in order to improve the transmission of the lens, we coat the lens so that its light transmission is increased from 90% to more than 98%. In order to achieve this effect, the coating procedure is designed with very precise calculations and practical effects. The design should focus on the degree of visible light transmission, increasing the transmission as much as possible for light waves from 450nm to 730nm, and for light waves on the second side can be disregarded because we are not sensitive to them with the naked eye. The final effect is that the light waves from 450 to 730 nm can achieve a transmission rate of more than 99%. The direct effect of doing so is to reduce reflections and increase clarity. For example, when the flash shines on the coated lens, there are almost no reflections, and conversely, the photo is white and you can’t see your big beautiful bright eyes. The initial production of coated lenses is green in color, mainly to distinguish them from non-coated lenses, and at the part of 515 nm, the reflection is enhanced, about 3-4%, so that the contrast is there and the reflection is seen in the green film. This film layer is the most standard reflective reduction film, the best and the oldest available. Later, in order to find a new competitive new product or selling point, the designers, changed the coating procedure to increase the reflectivity of the orchid light, while reducing the green reflectivity, there is the orchid film lens, this film has certain shortcomings: the reflection of the orchid light is too large, about 10-15%. This is not the intention of the designers to mention so high, in my design, I found that if the reflection of the blue light is lower than 5%, in the production process, the workers can not control the stability of the film color, for the production plant, it is necessary to achieve mass production, film color consistency. Such lenses, from the optical point of view, reduce the light transmission, and when there is light behind people, there will be a strong reflection, especially drivers are more unsuitable for such lenses. In night driving, there will be a clear ghosting of orchid or orchid horizontal lamp-like reflection. As for the red film, it increases the reflectivity of the red part, i.e. in the area of 700-780 nm, which also affects the light transmission, but it is a little better than the blue film, because we are not very sensitive to the red part. Gold film is to increase the reflection of red and yellow, which also affects the light transmission. It is not attached to the principle of optical use, it is just a decorative effect. In 2008, people have become aware of the optical effect of the coating, understand some basic knowledge, and have new insights into the choice of film color, there is a new generation of high transmittance film on the market: yellow-green film, the color is dark and light as the top product. The light transmission rate is 2% higher than the conventional green film. Therefore, the best film should have the maximum light transmission, extremely weak reflection, the lower the color the better.