偏振镜的作用

偏振镜的作用 The role of polarizing mirrors The polarization mirror is divided into round and line. Generally, the most commonly used is round, or CPL. The polarizing mirror is composed of two sets of lenses, which are polarized in different directions. When used, by adjusting the relative Angle of the two pieces of lens before and after the adjustment, the control of the incident light in one direction is achieved, and the reflection light in a particular direction is filtered out. Using polarizing mirrors, the sky will be dimmed and the entire image will appear dark, so the exposure will need to be increased by 1 ~ 2EV. Generally, the use of electronic viewfinder or LCD was filming, by rotating a polarizer in front of the lens, can clearly feel the reflected light decreases, frame the darkest time filter miscellaneous light effect is best. 1 \ polarizer is mainly used to eliminate the polarized light from the atmosphere, realize remove non-metallic surface reflective, such as glass surface, the surface of the water, polished surface, improve the color saturation, and so on, widely used in the flowers and landscapes. It features with a light resistance, so it can lead to cuts in 1-2 ev exposure. So many photographers will polarizer ACTS as a protector is inappropriate. The polarization mirror effect is most noticeable when it is on the right side of the light. 3 \ landscape photography needs to be reflected in the surface of the water to be unable to use polariscope, otherwise the water will be removed from the water. 4 \ because of the resistance of the polarization mirror to the light, the light and the shutter can be limited to the aperture and shutter, which is not good for controlling the vibration of the hand. The misuse of polarizing mirrors in photography can lead to excessive saturation, resulting in the loss of color and authenticity. In some special cases, such as a strong backlight shot into the lens, the polarization mirror causes a halo, which affects the sharpness of the image. The use of polarizer is obvious in the following situations: The reflection of the water surface can be removed from the surface of the water. The light from the sky will be removed, which will make the cloud more prominent. 3, the most obvious way to filter out the air is when the direction is 90 degrees. Polariscope, also called a polariscope, is a type of filter. Excellent use of polarizer is selectively let light through a direction vibration, in color and black and white photography often used to eliminate or weaken non-metallic surface strong reflection, to eliminate or reduce the light spot. For example, in the landscape and scenery photography, commonly used to represent strong reflective of the simple sense of objects, highlight the scenery behind the glass, pressure performance and dark sky and the blue sky white clouds. The two optical glass is sandwiched with a small, light-oriented crystal, such as mica. There is another kind of manufacturing method, the interlayer between the two pieces of optical glass coated with polyethylene film or polyethylene cyanide kind of crystal, the fence of the polymer coating can produce very fine structure, seems to be a close fence, only allow and gap of the same direction of vibration by light. Then the two pieces of glass independently installed in the loop can rotate, eliminated by rotating one of the lens can be taken polarization light reflected on the surface of the object. This layer of coating will decay gradually, and it will shorten the life span of the moisture and impact. In the end, the polymer-coated PL is consumable, not durable. In normal circumstances, it is ok to use five or six years. polarizer The light itself is a kind of electromagnetic wave, which is not really different from radio waves, but a shorter wavelength. After reflection and diffuse reflection, the vibration in one direction decreases, resulting in polarized light. According to the filtration mechanism of different polarized light, polarizer can be divided into circular polarizer (CPL) and linear polarizer (LPL), the role of these two are the same. LPL is mainly used for old-fashioned manual focusing cameras. Appear relatively late CPL increase a quarter wavelength of a layer of thin film, the film has a special nature, can be in one direction (assuming that x) as the polarization of the electric vector of PI / 2 phase shift, and the vertical direction with it (assuming y) electric vector does not have any effect. So you can make the above the Angle bisector of polarized along the x and y direction by 1/4 wave plate, so there are two kinds of exit is a beam of light polarization direction perpendicular to the phase difference of PI / 2 synthesis of polarized light, the light is circularly polarized light. This design makes it more suitable for new automatic focus and automatic exposure cameras. The CPL is currently used as a polariscope camera with an AF lens (automatic focus switching camera lens). In some light conditions, a linear polariscope is likely to mislead the optical component of the machine, so DC and most autofocus cameras use circular polariscope. The role of the polarization mirror The function of PL is to filter the reflection light and increase the contrast. It works by selectively filtering light from one direction. By filtering out many of the polarized light in the diffuse reflection, it reduces the intensity of light in the sky, darkens the sky, and increases the contrast between the blue sky and the cloud. The actual action is to look at the viewfinder and rotate the front mirror, the most obvious effect of the darkest hour in the viewfinder is 90 degrees. You can switch to any Angle between the darkest and the brightest. PL lens can effectively eliminate or decrease nonmetallic reflective surface, the reflected light is typical of polarized light, the metal surface reflected light is not polarized light, polarized lenses for it doesn't work), by adjusting the polarizer can filter out the part of the reflective, thus improve the subject quality of the object, and to increase the sharpness of the picture. For example, by using a polariscope, you can reduce the reflection of the water and make clear pictures of fish in the water. When shooting such a scene, the Angle of projection of the light source is the same as the camera Angle, and the maximum Angle of deflection should be between 30 and 40 degrees. Using the lens of the front of the filter, you can adjust it to minimize the reflection of the surface. In addition, polarizer can effectively improve the color saturation, to improve the contrast, this is because the polarizer can absorb the fog or dust in the atmosphere and light reflected from the direction of the various miscellaneous shoot the images to make more pure. For example, in photography such as taking a flower still, use a polariscope to make a colorful picture. It is useful for landscape photography, flower photography, and photographing certain types of reflective objects. A polariscope is an excellent effect of cloud painting when taking pictures of landscapes. The blue sky's refractive index is larger than that of the cloud. Using a polariscope can also make the green leaves more saturated and remove the shade of the city scene from a lower Angle. The polarizer is composed of the body of the lens and a backseat that is connected to it and rotates. The body of the lens consists of a very fine crystal glass. When rotating, the grating of the polarizing mirror blocks the polarized light that is not parallel to it. Therefore, the polarization mirror can control and select the number of reflected light that is parallel to it (the reflected light is polarized light). This is why the polarization mirror can eliminate or weaken the reflection of non-metallic surfaces. But most polarizations are a little bit blue. The same partial non-polarized light that is in the same direction as the polarized light will be blocked in the same way. In order to avoid the picture colour too insipid, want to add more than one more exposure quantity. The difference between the line and the circle There are two kinds of polarization mirrors. One is a linear polarization mirror, or ordinary polarizer, and the English symbol is PL. Don't be a circularly polarized mirror. The English logo is CPL. The color of OL is grey, and it can move the polarized direction of its polarizing direction by about 80 percent, while the line that causes the vertical vibration of its polarization is less than 1 percent. The CPL is grey in appearance, and is made up of a single wire polarizing mirror and a quarter of a wave plate (special birefringence material). The quarter wave plate optical axis and the line of the polarizer polarized light vibration direction to form a 45 ? Angle. The light is moving from one part of the polaroid to the opposite direction. The natural light that is being shot toward the circularly polarized mirror, After passing the polarizer and a quarter of a wave, it becomes a circular polarized light. Line according to the polarization direction of polarizer and 1/4 wave when the optical axis 45 ? Angle of relative orientation is different, can produce a right-handed circularly polarized light or left-hand circularly polarized light. The circularly polarized mirrors that are common in the market are: Toshiba, gajian, kengao, baogu, maloumi, nikon, hama etc. Generally speaking, a linear polarization mirror and a circularly polarized mirror can meet the basic requirements of photography. However, the PL will affect the light and auto focus, which is generally not suitable for a digital camera that is more automated. Because digital cameras now have automatic focus and automatic exposure, part of the light is reflected in the photometric component. If the light is out through a mirror reflection, and that half a reflector is a coating made of non-metallic materials, they are the reflection of the light is polarized light. Digital camera with higher degree of automation to use ordinary line polarizer, part information is light filter, which can potentially cause AE (AE), AF (AF) likely out of control. However, CPL works very well on such cameras. Choose the polarizer technique The CPL is more expensive than the PL, and if the camera can use PL, there is no need to buy the CPL. What about your own camera can use PL, try to know, the first test AF: turn the PL lens in different directions, half press the shutter release autofocus (some body have AF button). If you have a normal autofocus in any direction, you can use a PL lens to implement the AF function. If, on the other hand, an AF fails in one direction, you must buy the CPL. Reexperiment AE: after the lens in front of the lens, the vertical is measured against the uniform white wall. Rotate the mirror in a different direction to see if the light is changing. If there is a change, you can only buy the CPL. Because the polaroid can also reduce the exposure of 1 ~ 2, it can replace the function of ND2 and ND4 neutral greyscale in certain situations. With a polariscope need certain skills, such as shooting the sky, you can use the right hand thumb and index finger into 90 degrees direction, finger pointing in the direction of the sun, and the thumb is the best shooting direction. In addition, because of the polarizer at best polarization effect, lose 1/2 to 2 files of aperture, so need to compensate for exposure, typically add 1 to 2 profile exposure. For unable to filter out the reflective metal surface, can be in front of the light source and a big piece of polarizer, such metal reflecting light is polarized light, you can use the polarizer filter out the reflective metal surface. However, when doing portrait photography, it is best not to use a polariscope, because the lens can filter the reflection of the face, causing the face to lose the stereo feeling.