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[Concept]
Also called polarizer, referred to as PL lens, a color filter.
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【Function】
The light itself is an electromagnetic wave, after a vibration in the direction by the reflection and diffusion will be weakened, thus becoming polarized, and therefore, a smooth object of the reflective surface and the diffuse sky light is polarized, and the light will affect the photography imaging clarity.
Can choose to let a vibration in the direction of the light to pass through in both color and black-and-white photography is commonly used to eliminate or weaken the highly reflective of the non-metallic surface, so as to eliminate or reduce flare.
The polarizer can choose a direction of vibration of the light through, so reflective polarizer can weaken the surface, you can highlight the blue sky and the pressure of the dark sky, still photography and landscape photography, polarizer useful.
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[Structure]
1 consists of two optical glass sandwiching a directional effect of the nature of the micro polarizing crystals (such as mica).
2 another method of manufacturing a sandwich between two optical glass coated with a polyethylene film or polyethylene cyanide dispersoids This polymer coating may produce a fence-like structure of ultrafine, seems to be a fine fence, allowing only the vibration direction by the same light with the slits.
Furthermore, the two pieces of glass are each independently mounted in the ring can be rotated by rotation, wherein a lens surface of the subject is the polarization of the reflected light will be eliminated.
This layer of the coating will gradually aging failure, and moisture and impact, vibration will shorten the service life.
3 in the final analysis, the PL polymer coating consumables, not durable goods. Under normal circumstances, the use of five or six no problem.
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Classification
Linear polarizer (LPL) / circular polarizer (CPL)
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Linear polarizer (LPL)
LPL is mainly used for the old-fashioned manual focus cameras.
The LPL will affect metering and auto-focus digital camera with a higher degree of automation is generally not suitable for use.
The digital camera has autofocus and auto-exposure function on these cameras, part of the light is reflected to the metering element up.
If these light rays are reflected out through the half mirror, the half mirror coating made of a nonmetallic material that is polarized, the light reflected by them.
Digital camera with a higher degree of automation, using ordinary linear polarizer, some of the light will be filtered out, which may lead to the AE (automatic exposure) are not allowed to AF (autofocus) may be out of control.
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[Circular polarizer (CPL)
A circular polarizer can be regarded as composed of two parts:
The first part is an ordinary linear polarizer, a vibration direction of the polarized light filters.
After part so that through it polarized vibration direction rotates in a circle.
The special polarized called circularly polarized light, circularly polarized mirror, hence the name.
2 appears later increase in the CPL layer of 1/4 wavelength of the film, this film has a special nature, can be in one direction (assumed to be x) polarization electric vector generating the π / 2 phase shift, and with The electric vector of the vertical direction (assumed to be y) has no effect.
It is possible to make the direction of the angle bisector of the polarized light along the x and y by the 1/4 wave plate, and therefore the outgoing light is bunch two perpendicular to the polarization direction, the phase difference of π / 2 polarization combining light, also called The circularly polarized light.
This design makes it more suitable for the new auto-focus and auto-exposure camera.
3 present the camera using AF lens (auto-focus function switched the camera lens), use CPL as a polarizer.
In some lighting conditions, the linear polarizer may mislead the machine closed beta optical components metering, DC and most autofocus cameras use a circular polarizer.
CPL appearance of gray by a linear polarizer and a quarter-wave plate (a special birefringent material) glue.
A polarization vibration direction of the optical axis of the quarter wave plate and linear polarizer to form an angle of 45 °. The light from the linear polarizer period incident forward, since one end of the quarter-wave plate incident to reverse. Forward toward the the circularly polarized mirror the natural light, passed after the linear polarizer and a quarter-wave plate, that is circularly polarized.
According to the direction of polarization of the linear polarizer is different from the fourth paddles when the optical axis at a 45 ° angle relative orientation, can produce right-handed circularly polarized light or left-handed circularly polarized light.
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[Role]
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1 PL mirror role is to filter the reflected light, to increase the imaging contrast.
The working principle is selectively filtered light from one direction.
By filtering out many of the diffuse reflection polarized light, which weakened the intensity of light in the sky, the dark sky pressure and increase the contrast between the blue sky and white clouds.
Specific real shot to be looking at the viewfinder and rotate the front lens, the viewfinder when the sky is darkest, the most obvious effect of the darkest and most debut difference 90 degrees. You needed to go to the darkest and the brightest any angle.
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2 PL mirror can also be effectively reduced, or the elimination of non-metallic reflective surface, typical of such reflected light is polarized (metal surface reflected back light is not polarized light and polarized light microscopy did not respond), and by adjusting the polarizers on can be filtered out of this part of reflective, thereby improving the quality of the subject, and to improve the clarity of the screen.
For example, by using the polarizer, it is possible to weaken the surface of the reflective, thereby a clear picture of the fish in water.
Shooting this scene, the projection angle of the light source and the point of view of the camera to take pictures approaching the same, and its maximum deflection angle is between 30 to 40 degrees.
When used by the slowly rotating lens group before the filter to adjust the the scene surface of the reflective strive to minimize.
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Works
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Many polarized in the photography is harmful.
The glass surface of the reflected light, so that we take less glass window things inside the surface reflection light enable us to take less than the fish in water, leaves the surface of the reflection light to the leaves become white, and the like.
Clear sky blue sky in the sun at 90 degrees in the vertical direction scattering is polarized, it makes the blue sky becomes less deep.
If you eliminate these polarized many photos will appear more saturated colors, the picture is more clear.
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2. Called a polarizer to filter out polarized filters
Common polarizer called the linear polarizer (PL mirror).
Polarizer mounted to the front of the lens rotating polarizer carefully, harmful glare is minimized or even disappear, so you can take photos without glare.
If you shoot the blue sky, the sky would appear to be more blue, darker.
Polarizer than filtered out of the polarized light, and also non-polarized light in the same portions with the vibration direction of polarized light is filtered out. Therefore, the use of the polarizer, generally increase the amount of exposure of more than one file.
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3 in the camera, the AF (auto focus) and AE (Auto Exposure), a part of the light to be reflected to the metering element up.
If these light rays are reflected out through a half mirror, the half mirror is formed of non-metallic material coating is polarized, the light reflected by them.
In this type of camera, if you use ordinary linearly polarized mirror, through the lens polarized light incident on the half mirror, if the angle is right, normal reflection. If the angle is inappropriate, will no light is reflected. Therefore, AE may not be allowed, AF may not be valid.
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Some camera viewfinder LCD display.
Some camera's LCD display by light illumination through the lens. If the lens is to use a linear polarizer, this LCD monitor will fail.
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How to make a polarizer both to filter out harmful polarized light, it also enabled unpolarized light after light entering the lens polarizer?
In this case we must use a circular polarizer (CPL mirror).
Circularly polarized light for the vast majority of optical components, and non-polarized light, there is no difference, so that the circular polarization mirror can be used on any camera.
Using this principle, it is easy to identify a polarizer in the end PL, CPL.
Party polarizer lens installed near the eyes, through to see non-metallic reflective polarizer.
Rotate the polarizer to a certain angle, the reflector will significantly weaken or even disappear.
Polarizer, in turn, for the same experiments, PL mirror will see the same results, and CPL mirror and ordinary sunglasses.
If the two line polarizer overlap, is rotated to the mutually perpendicular directions in the polarized light through the first polarizer, the second polarizer completely filtering effect is completely opaque.
Rotation in which a light transmission rate will gradually increase, if a variable grayscale mirror (there may be a little color cast)
If one of the CPL, CPL must be placed behind! The front polarizer CPL, do not see this phenomenon.
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6 Many zoom lenses, especially the low-end of the zoom lens, often before rotating piece focusing.
This lens polarizer is very difficult: the camera is mounted in a solid tripod, one hand fixed focus ring, other hand rotating polarizer, the eyes but also the effect seen in the viewfinder.
If you regularly use a polarizer, especially like shooting landscapes, purchasing lens in addition to the price, image quality and other factors, whether the former film rotation is also an optional factors.
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Polarizer is not a panacea.
If the sun angle is inappropriate, non-metallic surface reflection glare polarized light component is very small.
For example, shooting leaves often can not eliminate all reflective. If the use of ultra-wide-angle lens, difficult to obtain consistent results in the screen.
Especially when shooting the sky, and the sun angle of 90 degrees direction pressure is very dark, almost no effect in the other direction, causing the sky color and brightness unevenness.
Shooting water, a portion of the surface is not reflective, while another part reflective strong. Polarizer due to the rotation part of a large thickness, used in a super-wide angle lens may stopper angle.
Polarizer is used, due to the need to rotate the filter, and should not use the hood, it should try to put the camera in shooting shadows.
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Line polarizer circular polarizer price difference.
Whether or not a camera using PL, to be determined by experiment.
First, determine the AF: rotation PL mirror to a different direction, and half-press the shutter opens AF (some body dedicated AF Start button).
Any direction can be normal auto-focus, this body is able to use PL lens AF function.
Conversely, if a certain direction AF failure, it must be later CPL mirror!
Re-test AE: The front of the lens mounted on PL mirror vertically against the uniform white walls metering.
The rotating the PL mirrors to different directions carefully observed metering values ??change. If there is a change, had to buy CPL! If the AE and AF are not the problem, the future does not plan to buy another body, it can buy a PL lens!
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[Select]
1. CPL If the camera can be used PL, there is no need to buy more expensive, relative to the PL CPL.
Own camera can use PL, test what you know
First test AF: turn to a different direction PL lens autofocus (some body dedicated AF button), half-press the shutter opens.
Any direction can be normal AF, this body is able to use PL lens AF function.
Conversely, if a direction AF malfunction, it must buy CPL; retested the AE: the lens front loaded PL mirror, vertical front uniform white walls metering. The rotating the PL mirrors to different directions carefully observed metering values ??change. If there is a change, they can only buy a CPL.
The polarizer can also reduce the exposure amount of 1 to 2 Draw, so in some cases can substitute ND2, ND4 A neutral gray mirror.
Good polarizer requires certain skills, such as shooting the sky, you can use the right hand to the thumb and index finger at 90 degrees to the direction of the index finger pointing to the sun, and the thumb direction is the best shooting direction.
Polarizer the best polarization effects, loss of 1/2 to 2 files aperture exposure compensation, generally increase 1-2 stalls amount of exposure can be.
Reflective surfaces can not be filtered out of the metal, it is possible to add a polarizer in front of a light source, so that the metal reflection of the light is polarized light, the metal surface was removed by filtration and reflective polarizers can be used.
5, but during portrait photography, it is best not to use polarized light microscopy and this polarizer filter out the reflection of the face, the human face loss of three-dimensional.
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【Use】
1, the clear blue sky, and want to shoot the blue sky bluer.
2, the clear blue sky, blue sky to all scenes are infected with a layer of blue. Want to eliminate the scene on the blue, making the scene more saturated.
When shooting underwater objects the surface reflective and not see the object. You want to take pictures of objects in the clean water, such as fish; want the water darker.
4, shooting still life, want to eliminate the reflective surface.
5, shot through the glass behind something.
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【Article is excerpted from: Baidu Encyclopedia】
【Network reprint / Just reference】
【Translation is by Goolge】
