For shooting, no filter should be the best. Especially when facing the light source, the glare brought by the UV lens will definitely affect the picture. The function of coating is to minimize glare. Multi-layer UV coating is to coat 6-8 layers of film on both sides of the lens to ensure a light transmittance of more than 95%. Therefore, it is recommended to buy multi-layer coatings with higher light transmittance for UV mirrors. Buying some UV is to minimize the adverse effects of UV on exposure and glare while protecting.

When it comes to protecting a lens, basically everyone needs a UV lens for protection. In daily use, as long as you are careful, the lens will generally not be stained, because the lens cover can be closed at any time. But there are still some when you are not careful. The lens is dirty and heartaches. Wiping is afraid of scratching the lens. And only use the lens cover. Once you find the fleeting beauty, you need to take time to remove the lens cover. It is easy to miss it. chance. As a result, a UV mirror has become a protective cover that everyone needs now. The UV lens is one of the necessary components of a lens. Its main function is to prevent ultraviolet rays, reduce the blue-violet light waves transmitted to the photosensitive material, make the distant view clear, and improve the contrast and color saturation of the distant view. Although the CCD and CMOS used in DSLRs are not as sensitive to ultraviolet light as film, we still recommend installing a high transmittance UV lens to protect the lens and avoid contamination or damage to the lens. Compared with the cheaper double-layer coating UV, the multi-layer coating UV has a higher light transmittance.

For some lenses, there is still a problem in installing a UV lens, that is, after adding a UV lens, there is no way to cover the lens cap. In this case, some people use a knife, file, etc. to cover the lens cap. The tool cuts down the screws on the side of the lens so that you can add the UV lens and cover the lens cap. However, this method has a certain risk, such an expensive thing, if it is missed, it can be miserable. The second method is to add a UV lens when shooting, usually take off the UV lens and cover with the original lens cap. Although it is a little troublesome, there is no risk after all!

Polarizer

The role of the polarizer is to eliminate harmful reflected light, such as light reflected from water or glass and other glossy surfaces, improve the clarity and expressiveness of the image, and increase color saturation. For example, it can make blue sky, green leaves, ridges and buildings, etc. The colors are more vivid. The most important point is that the effect created by the polarizer cannot be reproduced by PS, while other filters, such as light reduction, grayscale, soft focus, fog, and various colored filters, etc. The effect can basically be achieved through post-computer processing. Although the polarizer is only an optional filter, it is still indispensable for those who like landscape photography or are interested in photography creation.

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

Photographing is inseparable from light, and light is an electromagnetic wave, which can vibrate in any direction on a plane perpendicular to the direction of propagation. In general, natural light vibrates evenly in all directions. When the subject is non-metallic and has a smooth surface, under a certain natural light irradiation angle, the reflected light will not only vibrate evenly distributed in all directions, but also part of the light wave that vibrates in one direction. Light is called polarized light. These rays containing natural light and polarized light enter the camera through the camera lens to form an image. When we watch these shots, we often find that the glare formed by polarized light in the screen destroys the integrity of the picture. For example, when we are shooting the subject in the shop window, the subject in the shop window is not clear due to the reflection of the glass (polarized light); the green leaves of flowers shot at certain angles are gray and white; in landscape photography, the blue sky is shot. Not blue enough, there are ugly reflections on the water surface, etc. Therefore, in many cases, polarized light is harmful to photography. So how to solve the influence of polarized light on the camera? We can add a polarizer to solve this problem.

A polarizer is an additional lens attached to the camera lens that can eliminate or partially eliminate polarized light. Polarizers are generally made of polyvinyl alcohol film processed by iodine dip dyeing and glued between two flat optical glasses. 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 vibrates perpendicular to its polarization direction can only pass less than 1%. The color of the polarizer mirror is close to black, and the outer edge of the lens can be rotated. It consists of a lens body and a rear seat frame that is connected to it and can be rotated. The main body of the lens is a grating composed of extremely fine crystal glass. When rotating, this grating will block polarized light that is not parallel to it. Therefore, the polarizer can control and select the amount of reflected light parallel to it (this reflected light is polarized light) recorded on the film.

The polarizer is also a widely used additional lens. Its function is to effectively reduce or eliminate the reflection of non-metallic surfaces. The 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: eliminate or weaken the surface reflection of smooth objects; darken the sky tone; replace the neutral gray filter with two overlapping sheets; and increase the saturation of the color image, improve the contrast, and so on. For example, when shooting a water surface or a scene in a glass showcase, a polarizer can be used to eliminate the reflection on the surface, and the outer edge of the lens can be rotated during use until the reflection on the surface of the scene is invisible. There is also a big contrast between light and dark in the sea or outdoors where the sun is shining. You can use it to reduce the excessively bright parts, so that the light and dark parts of the picture can get a proper balance.

Although the polarizer is the most valuable filter in digital photography, it is not a panacea. When the polarizer removes large-area reflections, it also changes the light ratio of each part of the picture, so the color 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 highlights account for a large proportion of the screen, the use of a polarizer will affect the tone of other parts of the screen; if the shooting scene has a small proportion of the reflective highlights, there will be basically no change in the tone of the other parts of the screen In the case, increase the local color saturation. Under certain lighting conditions, the content of polarized light is very small. At this time, using a polarizer will not have the expected effect. At the same time, due to the increase of optical lenses in the optical path, it will have a negative effect on the image quality of the picture. At the same time, since the polarizer has a rotating part and a large thickness, it is easy to form a vignetting phenomenon, which requires attention during use.

There are many kinds of polarizers. According to the device mode, it can be divided into embedded type and exterior type; according to the working principle, it can be divided into linear polarizer (pl) and circular polarizer (cpl), so according to the characteristics of the camera, choose a suitable polarizer.

Among these polarizers, the most common are general exterior linear polarizers (pl) and circular polarizers (cpl). The polarizer is generally composed of two parts. The rear part is threaded to connect with the camera, and the front part has a filter part that can be rotated. By changing the angle of rotation, the passage of polarized light can be reduced. Its working principle can be simply understood as: before the natural light and polarized light in the reflected light of the subject enter the lens, under the action of pl, harmful polarized light is "filtered out", and the natural light part passes through and is "transformed" into polarization. Light, the light entering the lens is actually polarized light; under the action of cpl, the polarized light is "filtered out" by the reflected light, and the natural light part passes through and is changed into polarized light, and then the polarized light "rotates" once again, "shaking a change "It becomes natural light again, and the light entering the lens is actually natural light. Therefore, cpl is more complicated than pl, which is the main reason for the large price difference between the two, and the price of cpl 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 it is polarized light, and the light after passing through cpl is "natural light". The metering and focusing components in many cameras have non-metallic reflective surfaces. Obviously, if the light entering the lens is polarized light, the metering and focusing may be out of alignment. To overcome this shortcoming, cpl was designed. Although the light passing through the cpl is still polarized light, the polarization direction of the light will continue to change during propagation, which is equivalent to "natural light", thus ensuring the normal operation of the camera's metering and focusing system.

In the actual purchase of polarizers, it is found that many business sales staff can't distinguish between pl and cpl, so we need to make a judgment ourselves. Bring the polarizer close to your eyes and observe the reflection of non-metallic scenes. Turn the polarizer to a certain angle, and the reflection will weaken or even disappear; if the polarizer is reversed for the same experiment, the pl will see the same result, and the scene observed by the cpl There is basically no change.

Linear polarization is an ordinary polarizer. After the light passes through, it is in a state of a single polarization direction. Circular polarization is based on the linear polarization and a lens is added to make the polarized light into a circular polarization state, which can also be said to be no longer It is polarized light. It can be simply said: the light after linear polarization is polarized light, and the light after circular polarization is not polarized light. This is the biggest difference between them.

The specific adjustment method of the polarizer is as follows:

Install the polarizer directly on the front of the camera lens, while slowly rotating the polarizer, observe the polarized light source in the subject through the LCD screen or the viewfinder until it disappears or weakens to the expected effect; you can also use the polarizer first Place it directly in front of your eyes and rotate the polarizer while viewing the view until the polarized light disappears or weakens to the expected size. Then, under the premise that the orientation of the polarizer remains unchanged (that is, the direction indicated by the mark 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 position at will, otherwise the polarization direction of the polarizer must be readjusted.