心灵的玻璃窗 DV附加镜头纵横谈（The glass window of the heart, DV, additional lens, vertical and horizontal talk）

1、心灵的玻璃窗 DV附加镜头纵横谈（The glass window of the heart, DV, additional lens, vertical and horizontal talk）The glass window of the heart, DV, additional lens, vertical and horizontal talk12345, next page-2004-05-19 11:29 Xiao Jiantao (Cseek / day)Like digital cameras, digital cameras use additional lenses th

2、at can also be used for better shooting and special effects. Since DVs original lens is a non replaceable component, the DV can only be mounted in front of an existing lens in order to use additional lenses. DV with additional lenses, although there is no variety of cameras, but after recent years o

3、f development, the current market DV additional lens category is also very rich. Here are some of our commonly used DV additional lenses.A, USAIn fact, it is ultraviolet UV filters, the following two functions:The first is to prevent ultraviolet rays. Is the suns ultraviolet wavelength 200 - 400 nm

4、radiation, it is also a kind of sunlight in the shortest wavelength, the rays of our naked eye is invisible, but it can make the film and photo sensitive material phenomenon, reduces the photographed image color Xian Yancheng. This time we use a UV filter can filter out the UV, blue violet to reduce

5、 transmission wave on a photosensitive material, make clear vision, improve the far scenery contrast and color saturation. In some special occasions, such as the plateau, with a very strong ultraviolet, UV is very necessary.Second is to protect the DV lens. Since most of the DV lens are exposed, so

6、it is easy to be polluted by dust, water, oil or fingerprints, which we need to frequently wipe the lens, DV lens is very delicate, but caused a mirror wear is difficult to recover, it will seriously affect the clarity of the picture and quality. In addition not careful in peacetime when using colli

7、sion with foreign body contact, will cause irreparable consequences. Therefore, the installation of a transparent UV protective lens outside the lens can protect the lens from being directly contaminated or damaged. In some special occasions, such as water, moisture large space, especially in the ac

8、cident scene, shooting environment or sandstorm weather bad, because many uncertain factors may lead to the lens with a UV damage, then can protect the lens is very good, as long as a good rub shot UV can instead, carefully wipe the always on tenterhooks, expensive camera!UV can be said to be one of

9、 the most widely used the additional lens. Now it also has some controversy, some people think that the USA is often a piece of glass, but only some high transmittance. Theoretically, UV should filter ultraviolet light, so as to form a protection of the lens in bright light. But if the ability to fi

10、lter out ultraviolet light is too strong, then often will also shield part of visible light, reduce the amount of light into the lens. Moreover, UV light is generally not strong enough to affect CCD sensitization or damage to CCD. So the effect of UV meaning does not seem too big. Of course, anyway,

11、 if you want to shot a long time at the suns another shot. According to a veteran, home what DV does much need to add some television stations in the USA, hundreds of thousands of machines are not added. Ha-ha！ Its the public stuff, nobody loves it, but home DV is yours! In fact, we use the biggest

12、role is to prevent the UV Lens pollution and accidental scratch. Especially DV is different from camera, it works continuously and takes a long time, so the protection of lens is more important, especially in abominable shooting environment or sand wind weather.For some DV with UV also exists a prob

13、lem that after adding UV has no way to cover the lens cover, in this case, some people in order to cover the lens cover, knife, file tools such as the lens on the edge of the screw cut short,This can not only add UV, and cover the lens cap. However, this method is a certain risk, so expensive things

14、, in case of missing, can be miserable. The second method is the camera with UV, usually off UV lens, cover the original lens cover, although some trouble, but it has no risk!DV and UV can be said to be inseparable, UV is generally random purchase, and then tighten the lens in front. The production

15、has the function of UV filter UV also has a certain degree of difficulty, the main difficulty is to filter out ultraviolet light, the lens and the lens will be yellow; absolutely colorless and transparent, the UV filter effect will decrease. Therefore, choose the most important standard for UV light

16、 is visible light rate is high, it is best to use with multilayer coating type, so the imaging quality will not have much impact, ordinary window glass do UV backlight when shooting more prone to glare. The choice depends on the diameter of UV, the purchase in accordance with the caliber size of the

17、 lens labels such as 37mm or 30mm to buy a digital camera, to match their attention and. Dont buy that kind of low price and poor quality products, not only because of poor effect of UV telephoto zoom lens focus, can not play the role of UV blocking, seriously affect the image quality of the zoom le

18、ns, the focus deviation caused by blurred images. Another is to make a simple color choice between silver and black.The glass window of the heart, DV, additional lens, vertical and horizontal talkLast page, 12345, next page-2004-05-19 11:29 Xiao Jiantao (Cseek / day)Two polarizing mirrorTo understan

19、d the polarizer, we first need to know what polarized light is.Photography can not be separated from light, and light is also an electromagnetic wave, which can vibrate in any direction in the direction perpendicular to the direction of propagation. In general, natural light is uniformly distributed

20、 in all directions. When the object is non metal and have smooth surface, in natural light irradiation angle is constant, the reflected light in all directions vibration of uniform distribution of natural light, some concentrated light vibration in one direction, this part is called polarized light.

21、 These light rays, which contain natural light and polarized light, enter the camera through the lens of the camera and form an image. When we watch these pictures, we often find that the glare of polarized light in the picture destroys the perfection of the picture. For example, we in the subject i

22、n the window, the glass reflector (polarized light) to the window subject is not clear; some angle flower green leaves gray, pale; in landscape photography, shooting the blue sky blue water is not enough, very ugly reflection. Therefore, polarized light is harmful to photography in many cases. So ho

23、w can we solve the effect of polarized light on photography? We can add a polarizer to solve this problem.A polarizer is an additional mirror attached to a camera lens to eliminate or partially eliminate polarized light. The polarizer is usually made of a polyvinyl alcohol film made by iodine impreg

24、nation and glued between two plates of optical glass. It can let the linearly polarized light with its polarization direction go through about 80% of the light intensity, while the linearly polarized light with its polarization direction can only be less than 1%. The color of the polarizer mirror is

25、 close to black, and the outer edge of the polarizer can be rotated. The utility model is composed of a lens main body and a back seat frame which is connected with the lens body and can rotate. The main body of the lens is made of very fine crystal glass. When rotating, the grating blocks polarized

26、 light that is not parallel to it. Thus, the polarizer is capable of controlling and selecting the number of reflected light reflected parallel to the film (the reflected light is polarized).Polarizer is also a widely used additional lens.Its function is to effectively reduce or eliminate the non me

27、tallic surface reflection. Polarizer can be used in black and white and color photography, because it can reduce the brightness of light, so its appearance is gray. The polarizer is often used in these situations: reflective surface to eliminate or weaken the smooth objects; the sky darkened two ton

28、es; overlapping instead of grey filter; and improve the color image saturation, increase the contrast and so on. For example, in the shooting of water or glass window of the scene, you can use the polarizer to eliminate surface reflection, use the rotating lens outer edge until you can not see the r

29、eflection of the surface of the scene. And in sunny beach or outdoor shade, a great contrast, it can be used to reduce excessive brightness, let light picture moderate balance part.Although the polarizer is the most valuable filter in digital photography, it is not omnipotent. The polarizer changes

30、the light ratio of each part of the picture when it removes large areas of light reflection, so the color of the picture taken with a polarizer will change somewhat. For some scenes, whether or not to use a polarizer depends on the specific needs of the individual. When the reflective Gao Guangzhan

31、screen ratio is larger, with the polarizer will have an impact on other parts of the tone of the picture; if the shooting scene in the picture when the proportion of reflective Gao Guangzhan, will be in other parts of the basic tone of the picture without changing circumstances, improve the local co

32、lor saturation. In some lighting conditions, the content of polarized light is very small, so the polarizer will not achieve the desired effect at the same time, but because of the increase of optical lenses in the optical path, it will have a negative effect on the quality of the picture. At the sa

33、me time, due to the polarizer has a rotating part, the thickness is large, easy to form dark angle phenomenon, need to pay attention to in use.There are many kinds of polarizers. According to the device, it can be divided into embedded and external type. According to the principle of work, it can be

34、 divided into linear polarization mirror (P L) and circular polarization mirror (CPL). Therefore, the appropriate polarizer should be chosen according to the characteristics of the camera.In these polarizing mirrors, the most common ones are the general external linear polarizer (PL) and the circula

35、r polarization mirror (CPL). A polarizer is usually made up of two parts. The back is threaded and connected to the camera. The front part has a filter section that rotates to reduce the passing of polarized light by varying the angle of rotation. Its working principle can be understood as a simple:

36、 natural light and polarized object reflected light in front of the camera, in the presence of PL, the filter, polarized light is harmful to natural light and part through the transformation is polarized, incoming light is actually polarized light; reflected light in C P L under the action of polari

37、zed light is filtering, natural light and polarized part through the change, and then polarized circle rotation, change has become a natural light, the light entering the lens as natural light. Therefore, CPL is more complex than PL, which is the main reason for the big difference in price between t

38、he two, and the price of CPL is higher. The difference between PL and CPL can be simply understood: no matter what kind of light passes through PL, the light is polarized, and the light after CPL is natural light. In many cameras, the metering and focusing component has a non metallic reflector. Obv

39、iously, if the light entering the lens is polarized light, the metering and focusing error may be made possible. To overcome this shortcoming, CPL was designed. Although the light of CPL is still polarized light, the polarization of light will change in propagation, which is equivalent to natural li

40、ght. Therefore, it can guarantee the cameras photometry and the normal operation of the focusing system.Found in the actual purchase of polarizer, a lot of business sales staff fenbuqingchu PL and CPL, so we need to own a place of judgment. The mirror close to the eyes, observe the metal scene refle

41、ctive polarizer to rotate at a certain angle, reflection will weaken or even disappear; the polarizer in turn do the same experiment, PL will see the same results, and observed by CPL scene is not change.The specific adjustment method of polarizer is as follows:The polarizer is mounted directly at t

42、he front of the camera lens,While slowly rotating polarizer, while through the LCD screen or the viewfinder observation photographed the scene in the polarized light source, until it disappeared or reduced to the expected effect so far; it can be placed directly in front of the first polarizer, whil

43、e viewing while rotating polarizer, polarized light until the reduction or disappearance of the expected size to date. Then, when the azimuth of the polarizer remains constant (i.e., the direction indicated by the mark on the edge of the polarizer remains constant), the polarizer is shifted and plac

44、ed in front of the camera lens. After that, the camera can not change the shooting position at random, otherwise, the polarization direction of the polarizer must be re adjusted.The glass window of the heart, DV, additional lens, vertical and horizontal talkLast page, 12345, next page-2004-05-19 11:

45、29 Xiao Jiantao (Cseek / day)Three 、 wide-angle lens and range mirrorSince the DV cannot change lenses as freely as a camera, its lens zoom ability has been limited to death at the time of production. Although DV zoom has now reached 10 times or more, but sometimes it is still insufficient. Then, if

46、 you cant change the lens, you can only use the additional lens to increase its zoom ability. This is also the use of wide angle lenses and range lenses. In general, a wide angle mirror reduces the focal length to a fraction of the original, and the zoom lens also increases the focal length to sever

47、al times. Usually two times, although there are also more magnification and wide-angle lenses, but in general shooting, two times enough. However, as additional lenses cause loss of light, the number is as low as possible.1. external wide-angle lensGenerally, the DV lens has a narrower view angle. U

48、sually, the standard lens has a coverage angle of about 47 degrees. It can provide an insight into the traditional painting we are used to. However, when any three-dimensional object is recorded on a two dimensional plane, it is bound to deform. As the coverage angle of the lens is enlarged, the ext

49、ended lines of perspective converge more and more to the horizon, and as the close range becomes larger, the depth is strengthened. Angular deformation, perspective exaggeration, and depth of field increase these effects, which make the camera more creative. In addition, in the narrow space of the i

50、nterior or limited, want to shoot a complete panoramic picture actually has its difficulties, so the general factory will produce some of the available collocation external wide-angle lens, for consumers, in order to increase the camera angle of view.To sum up, wide-angle lens should be used in the

51、following circumstances: (1) when shooting narrow place, and no retreat Road, but to take a lot of characters or scenery, use wide-angle lens. (2) when we need to enhance the perspective effect, such as the larger scenery in front and the smaller distance in the distance, we can use wide-angle lens

52、to make the depth of the picture feel larger than the standard lens. (3) in the process of moving shooting. Wide-angle lenses should be used as far as possible.2. externally coupled range mirrorWhen shooting, you need to zoom in on the distant scenes, which can be achieved with a larger zoom, plus a

53、 telephoto lens in front of the camera. The range mirror is also called a magnifying glass, and the range mirror is between the body and the standard lens. It can focus the camera several times as much as possible, so as to achieve the effect of narrowing and amplifying the scene. The advantage of t

54、he range mirror is its low cost and light weight, and its disadvantage is that it reduces the image quality. For example, when using a two - time range lens, the aperture of the standard lens is reduced by two times, so the aperture index should be reduced by two times accordingly.The range mirror c

55、an not be imaged alone, but after adapting to the main lens, the range of the main lens can be enlarged, and the images with different viewing angles and different image magnification can be photographed. The adaptation of the telephoto lens increases the focal length of the photographic lens, and b

56、asically does not affect the nearest focus distance of the main lens. So,Closest focusing distance increase from the mirror and the main lens optical system consisting of the value, generally higher than the lens of the same focal length much closer.Digital cameras generally have a small body, and t

57、he range of optical zoom lenses is not very large. When you need to follow a distant scene, you need to install a doubling lens. If your cameras optical zoom ratio is about 20 times, its not necessary to add an extra lens to your home unless you need it. If the range mirror is divided by the manufac

58、turer, it can be divided into general type and special type. Most independent lens manufacturers are generic, suitable for all kinds of telephoto lens, the price is generally cheaper. But the DV manufacturer produces the special-purpose type to increase the distance mirror to be able to be better, but the price is higher.The following points should be paid attention to in the adaptation and use of the range mirror: (1) no matter how excellent the optical performance is, the excellent range mirr