Knowledge points of filters and the history of lens coating development
Because of the obvious performance advantages of the filter, the filter is very useful, widely used in the photography industry, and often used as a filter. Let's take a look at some of the knowledge points of the filter used as a filter.
1. Ultraviolet filter is also called UV lens. Its function is to absorb ultraviolet light and a small amount of blue ultraviolet light invisible to human eyes, reduce fog and increase the distance of the mouth. The clarity of the scene. In addition, it also plays a role in protecting the lens from water and dust.
2, the polarizer is also called the polarizer, and the angle needs to be adjusted when using it to eliminate the polarized light. The main functions of the polarizer are: eliminate the reflection of non-metallic surfaces; darken the blue sky and deepen its hue; increase the color saturation of the subject; because the polarizer is gray, it also plays a role in blocking light, thereby Used as a gray density mirror.
Optical lens 3. Soft lens is also called soft focus lens. The lens is colorless and transparent, and the surface is corroded with different density and density patterns, which can cause the light beam to scatter, thereby Play a softening effect. Soft lenses are often used when shooting portraits.
4. Special effect filters are some of the normal effects that can change the image and make the screen show a variety of wonderful changes. Such as starlight mirrors, multi-shadow mirrors, hollow mirrors, dynamic mirrors and various magic mirrors.
When a filter is equipped, an adapter ring or an adapter barrel is needed. Here is a problem of the diameter of the UV lens. The diameter of the filter (protective lens) is usually 46, 49, 52, 55, 58, 62, 67, 72, 77 (units are mm), etc., and filters with specifications like 82, 86, 95, 105 Mirrors are usually used by professionals, and they are not very common in market optical lenses. When choosing a caliber, we need to consider the following two aspects-the situation of blocking flash and the situation of vignetting. Generally speaking, the larger the caliber, the more expensive the lens is (46) mm, the easier it is to block flash, but at the same time it is not easy to have vignetting; the smaller the caliber, the opposite is the case, it is not easy to flash but it is easy to darken. Angle, but the lens is cheap.
Anti-wear film began in the early 1970s. At that time, it was believed that glass lenses were not easy to grind because of their high hardness, while organic lenses were too soft and were easy to wear. Therefore, the quartz material is plated on the surface of the organic lens under vacuum conditions to form a very hard wear-resistant film. However, due to the mismatch between its thermal expansion coefficient and the base material, it is easy to peel off and the film is brittle, so it is resistant to The wear effect is not ideal.
After focusing on the lens in the 1980s, researchers theoretically found that the mechanism of wear is not only related to hardness, but the film material has the dual characteristics of 'hardness/deformation' , That is, some materials have higher hardness but less deformation, and some materials have lower hardness but greater deformation.
The second generation of anti-wear film technology is to coat the surface of the organic lens with a material with high hardness and not easy to brittle through the immersion process.
The third generation of anti-wear film technology was developed after the 1990s, mainly to solve the problem of abrasion resistance after the organic lens is coated with an anti-reflection film. . Since the hardness of the organic lens base and the hardness of the anti-reflective coating are quite different, the new theory believes that there needs to be an anti-wear coating between the two, so that the lens can act as a buffer when it is rubbed by grit. It is not easy to produce aspherical mirror marks.
The hardness of the third-generation anti-wear film material is between the hardness of the anti-reflection film and the lens base, and its friction coefficient is low and it is not easy to be brittle.
The fourth-generation anti-film technology uses silicon atoms. For example, the French Essilor TITUS hardening fluid contains both organic matrix and Containing inorganic ultrafine particles including silicon, the anti-wear film has toughness and at the same time increases the hardness.
The most important thing in modern anti-wear coating technology is the immersion method, that is, the lens is immersed in a hardened liquid after multiple cleanings, and after a certain period of time, a certain amount of The speed is lifted.
This speed is related to the viscosity of the hardening fluid and plays a decisive role in the thickness of the anti-wear film. After lifting, polymerize in an oven at about 100°C for 4 to 5 hours, and the coating thickness is about 3 to 5 microns.