For shooting, no filters should be the best. Especially when facing the light source, the glare brought by the UV mirror will definitely affect the picture. The role of the coating is to minimize the generation of glare. Multi-layer coating UV is plated 6-8 layers on each side of the lens to ensure that there is more than 95% light transmission. Therefore, it is recommended to buy a multilayer coating with higher light transmittance for UV mirrors. Buy some UV in order to minimize the adverse effects of UV on exposure and glare while protecting.

When it comes to protective lenses, basically everyone will need a UV mirror to act as a protective effect. In daily use, as long as care is taken, the lens is generally not stained, because the lens cap can be closed at any time. But there are still some careless, the lens dirty heartache, wipe and afraid of scratching the lens, and only the lens cap, once found fleeting beauty, but also spend time to remove the lens cap, it is easy to miss a good opportunity. Therefore, a UV mirror has become the protective cover that everyone needs now. UV mirror is one of the necessary components of a lens, its main role is to prevent ultraviolet light, reduce the transmission of blue-violet light waves on the sensitive material, make the distant view clear, improve the contrast and color saturation of the distant scene. Although the CCDS and CMOS used in DSLRS today are not as sensitive to ultraviolet light as film, we recommend installing a UV lens with high light transmission to protect the lens from contamination or damage. Multilayer coated UV has a higher transmittance than the cheaper double-layer coated UV.

For some lenses, there is still a problem with the addition of UV mirrors, that is, there is no way to cover the lens cap after the UV mirror, in this case, some people in order to cover the lens cap, use knives, files and other tools to saw the screw on the side of the lens short, so that you can add UV mirrors and cover the lens cap. However, this method has a certain risk, such an expensive thing, in case you miss it can be miserable. The second method is to add a UV mirror when filming, usually take off the UV mirror, cover the original lens cover, although some trouble, but this is no risk!

polariscope

The function of the polarizer is to eliminate harmful reflected light, such as light reflected from shiny surfaces such as water or glass, improve the clarity and expression of the image, and increase the color saturation, such as it can make the blue sky, green leaves, ridges and buildings more vivid. The most important point is that the effect created by the polarizer can not be reproduced with PS, and other filters, such as reducing mirrors, gray mirrors, soft focus mirrors, atomizing mirrors, and various color filters can be basically achieved through computer processing in the later period. Although the polarizer is only used as an optional filter, it is indispensable for those who like landscape photography or are interested in photography creation.

To understand polarizers, we first need to know what polarized light is.

Light is an electromagnetic wave that can vibrate in any direction on a plane perpendicular to the direction of propagation. Under normal circumstances, the vibration of natural light is evenly distributed in all directions. When the subject is non-metallic and has a smooth surface, under a certain natural light irradiation Angle, the reflected light in addition to the natural light that vibrates evenly in all directions, some of the light waves are concentrated in one direction, and this part of the light is called polarized light. This light, which contains both natural and polarized light, enters the camera through the lens and forms an image. When we watch these pictures, we often find that the glare formed by polarized light in the picture destroys the perfection of the picture. For example, when we shoot the subject in the window, due to the reflection (polarized light) of the glass, the subject in the window is not clear; The green leaves of flowers photographed from some angles are gray or white; In landscape photography, the blue sky is not blue enough, the water has a very ugly reflection and so on. Therefore, in many cases, polarized light is harmful to photography. So how to solve the impact of polarized light on the camera? We can fix this by adding a polarizer.

A polarizer is an additional mirror attached to a camera lens that can eliminate or partially eliminate polarized light. The polarizer is generally made of iodine impregnated processed polyvinyl alcohol film, glued between two flat optical glass. It allows linearly polarized light that is in the same direction of its polarization to pass through about 80% of the light intensity, while linearly polarized light that is vibrating perpendicular to its polarization direction can pass through less than 1%. The polarizer mirror color is close to black, and the outer edge of the lens can be rotated. It consists of a lens body and a backseat frame connected to it that can be rotated. The body of the lens consists of extremely fine crystal glass to form a grating. When rotated, this grating blocks polarized light that is not parallel to it. Thus, the polarizer is able to control and select the amount of reflected light (this reflected light is polarized light) that is recorded parallel to it on the film.

Polariscope is also a widely used additional lens. Its function is to effectively reduce or eliminate the reflection of non-metallic surfaces. Polarizer can be used in both black and white and color photography, because it can reduce the brightness of the light, so its appearance is gray. Polarizers are often used in the following situations: to eliminate or reduce the surface reflection of smooth objects; To darken the sky; Two overlapping instead of medium gray filter; And improve color image saturation, improve contrast and so on. For example, when photographing the scenery on the water surface or in the glass window, the polarizer can be used to eliminate the reflection on the surface. Also in the sunny seaside or outdoor, the contrast between light and dark is very large, it can be used to reduce the brightness of the excessive part, so that the light and dark part of the picture to obtain a moderate balance.

Although polariscope is the most valuable filter in digital photography, it is not a panacea. When the polarizer removes a large area of reflection, it also changes the light ratio of each part of the picture, so the tone of the picture taken with the polarizer will have some changes. For some scenes, whether to use a polarizer depends on the specific needs of the individual. When the reflective highlight accounts for a large proportion of the screen, the use of polarizer will affect the tone of other parts of the screen; If the proportion of reflective highlights in the shot scene is small, it will increase the local color saturation when the hue of the other parts of the picture is basically unchanged. In some lighting conditions, the polarized light content is very small, at this time the use of polarizers will not play the expected effect, and due to the increase in the optical lens in the light path, it will have a negative effect on the picture quality. At the same time, because the polarizer has a rotating part, the thickness is large, and it is easy to form a dark Angle phenomenon, which needs to be paid attention to in use.

There are many kinds of polarizers. According to the device mode can be divided into embedded type and external type; According to the working principle, it is divided into linear polarizer (p l) and circular polarizer (cpl), so the suitable polarizer should be selected according to the characteristics of the camera.

Among these polarizers, the most common are general external linear polarizers (pl) and circular polarizers (cpl). The polarizer is generally composed of two parts, the rear with a thread connected to the camera, the front with a filter part can be rotated, by changing the rotation Angle to reduce the passage of polarized light. The working principle can be simply understood as follows: before the natural light and polarized light reflected by the subject enter the lens, under the action of pl, the harmful polarized light is "filtered", the natural light part passes through and is "transformed" into polarized light, and the light entering the lens is actually polarized light; Under the action of the reflected light, the polarized light is "filtered", the natural light part passes through and is changed into polarized light, and then the polarized light is "rotated in a circle", "transformed" and becomes natural light, and the light entering the lens is actually natural light. Therefore, cpl is more complex than pl, which is the main reason for the large price difference between the two, cpl's price is higher. The difference between pl and cpl can be simply understood as: no matter what kind of light passes through pl, the light after cpl is polarized light, and the light after CPL is "natural light". Many cameras in the metering, focusing components have non-metal reflective surface, obviously if the light entering the lens is polarized light, it may make metering, focusing misalignment. cpl is designed to overcome this shortcoming. Although the light through the cpl is still polarized light, the polarization direction of the light will constantly change in the propagation, which is equivalent to "natural light", so it ensures the normal work of the camera metering and focusing system.

In the actual purchase of polarizer found that many business sales staff can not distinguish between pl and cpl, so we need to judge it ourselves. Put the polarizer close to the eye, observe the reflection of the non-metal scene, turn the polarizer to a certain Angle, the reflection will weaken or even disappear; Do the same experiment with the polarizer in reverse, pl will see the same result, while the scene observed with cpl will be basically unchanged.

Line bias is an ordinary polarizer, the light is in a single polarization direction after passing through the state, circular bias is on the basis of the online bias plus a lens, so that the polarized light into a circular polarization state, can also be said to be no longer polarized light. It can be simply said that the light after the line deviation is polarized light, and the light after the circle deviation is not polarized light, which is the biggest difference between them.

The specific adjustment methods of the polarizer are as follows:

Install the polarizer directly on the front end of the camera lens, rotate the polarizer slowly, and observe the polarized light source in the subject through the LCD screen or viewfinder until it disappears or weakens to the desired effect; You can also place the polarizer directly in front of your eyes and rotate the polarizer while viewing until the polarized light disappears or diminishes to the desired size. Then, on the premise that the orientation of the polarizer remains unchanged (that is, the direction indicated by the sign on the edge of the polarizer remains unchanged), the polarizer is translated and placed on the front end of the photographic lens. After that, the camera cannot change the shooting orientation at will, otherwise the polarization direction of the polarizer must be readjusted.