Apa Itu Lensa Polarized?
Artikel ini menjawab pertanyaan di shoutmix yang yang disamping yang ditanyakan mas Ongky, 2 januari 2009 lalu, tentang keuntungan dan kekurangan lensa polaroid, atau polarized.
Namun karena saya mau nulis sendiri kurang banyak materinya, akhirnya saya ambilkan dari www.wisegeek.com, dan ditambahin sedikit – sedikit, berikut artikelnya:
Polarized lenses are used in sunglasses to reduce glare from reflective surfaces such as the surface of a lake or the hood of a car. They accomplish this feat through a process called polarization, much like a venetian blind controls sunlight through a window.
Sunlight itself is not polarized – light from the sun will either be absorbed or reflected horizontally, diagonally or vertically. The problem this causes for fishermen and drivers lies in the horizontal reflectivity. Sunlight bouncing off a horizontal surface will strike the viewer’s eyes at a similar angle. This means the glare from the surface of the water or the road or the car hood will be strong. Polarized lenses have a laminated surface containing vertical stripes. These stripes only allow vertically-polarized light to enter the wearer’s eyes. Glare is eliminated because the horizontally-polarized lightwaves cannot bypass the polarized filter.
Polarized lenses do not provide universal protection from glare, however. If the wearer tilts his head past 45 degrees or so, some of the horizontal light can enter and cause some bright spots. Some wearers who use polarized lenses in snowy areas may find that they lose some contrast between snow and shadows. Fishermen and drivers seem to derive the most benefit from polarized lenses because they deal with mostly horizontal surfaces. A fishermen wearing polarized sunglasses can see below the surface of the water to search for schools of fish or hidden obstacles. Drivers are no longer affected by a constant reflection of light from their hoods or the road ahead.
There are some limitations to the use of polarized lenses, however. Because the polarizing stripes reduce the amount of light entering the eye, polarized lenses cannot be used for regular eyewear with clear lenses. Prescription sunglasses can be tinted a very light gray to accommodate the polarized laminate, but most contact lenses cannot. Some drivers discover that polarized lenses can cause distortions in liquid crystal displays (LCDs). Onboard clocks and other instrument displays may be temporarily unreadable.
Both horizontally and vertically-polarized lenses are used to view three-dimensional movies. Some of the light reflected from the movie screen is vertically polarized, which means only a lens with a similar vertical laminate will receive it. The other lens only receives horizontal lightwaves. Your brain takes both of these images and combines them to create a realistic sense of depth.
Sedang kalau lensa polarized itu dipakai sebagai lensa sunglass maka artikelnya ada di bawah ini:
Polarized sunglasses are designed to reduce the glare from surfaces like water, snow, and glass. They can be highly useful for sports, driving, and fishing by helping the participant in these activities to see more clearly, allowing for the avoidance of potential hazards. While they may be somewhat more expensive than conventional sunglasses, some consumers prefer polarized sunglasses because they selectively block out glare, rather than making the whole field of vision dimmer, which can be dangerous in some situations.
Light has many interesting properties, especially when reflected from another surface. Polarized sunglasses take advantage of one of these properties, known as polarization. Normally, a light source produces waves which go in all directions. When light is bounced from a surface like glass, water, or snow, the light waves polarize, meaning that they orient along an axis, which is usually horizontally. A vertical polarizing lens can reduce the brightness of these light waves while still allowing optical information through.
Because of their vertical polarizing orientation, polarized sunglasses are ideal for dealing with reflective glare conditions, depending on the angle. Experimentation with polarized sunglasses can yield an angle at which no light is filtered out, because the glasses are horizontally aligned along with the glare. At other angles, polarized sunglasses will filter out some or all of the glare, allowing the wearer to see with comfort and without potential eye strain. Polarized sunglasses are unfortunately not as useful when the sun is directly overhead or low to the horizon, because the angle of the reflected light waves changes from this horizontal configuration.
Polarized sunglasses are primarily used in situations where the wearer needs to be able to clearly see, but also needs to have dangerous glare filtered out. Glare makes vision difficult because the light hurts the eye and obscures details which may be hidden behind it. Conventional sunglasses will block out glare, but they will also block out subtle details about the wearer’s environment which may be dangerous. These polarized sunglasses designed for outdoor use usually come in a variety of configurations from very lightly tinted and mildly polarizing to heavily tinted and strongly polarizing. Some also integrate color tinting for visibility in specific conditions such as snow.
Some 3-D movies also use polarizing glasses. Usually one lens is horizontally polarized and the other one is vertically polarized, so that each eye sees a slightly different version of the movie screen. The eyes attempt to reconcile the two images for the brain, and the result is the illusion of a three dimensional image. Experimenters with several spare pairs of 3-D glasses lying around can play with the effects of polarization for themselves.
Untuk pertanyaan tentang kelebihan dan kekurangannya sudah ada di atas, namun yang utama dari kelebihannya adalah bisa untuk mengurangi glare atau silau dan membuat penglihatan lebih tajam atau lebih kontras, ini juga sangat membantu para driver pengemudi dimana anda bisa lihat kalau sudah sang terik matahari dan berjalan di atas aspal ada seperti fatamorgana dan silau, nah dengan lensa polarized bisa minimal atau hilang.
Nah, kalau kekurangannya, lensa ini jarang dipasang di lensa minus, namun sekarang udah ada dan akan ada warna sekitar 10-15 % grey begitu. Juga kalau kita melihat LCD sepeprti mesin EDC yang menggunakan layar LCD atau monitor bisa membuat tampilanannya terdistrosi, beberapa orang yang pernah saya ketahui waktu dioptik dulu ada yang melihatnya jadi aneh saat berhadapan langsung dengan kaca mobil mereka yang diberi lapisan film.
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