Sunglasses

Sunglasses or sun glasses are a visual aid, variously termed spectacles or glasses, which have lenses that are colored or darkened to prevent strong light from reaching the eyes. In the twentieth century were also known as sun cheaters (or simply cheaters).

<a href = "http://www.himfr.com/buy-Checked_Shirt/"> Checked Shirt </ a> Many people find direct sunlight too bright to be comfortable. During outdoor activities, the human eye can receive more light than usual. Health professionals recommend eye protection whenever outside to protect the eyes from ultraviolet radiation, which can lead to development of a cataract. Sunglasses have also been associated with celebrities and film actors primarily due to a desire to hide or mask their identity, but this also may be partly due to the fact that film lighting is typically stronger than natural light and uncomfortable to the unprotected eye. Since the early 1940 sunglasses have been popular as a fashion accessory, especially on the beach.

It is said that the Roman emperor Nero liked to watch gladiator fights Emerald. These, however, seem to have worked rather like mirrors. [1] Flat panes of smoky quartz which offered no corrective powers but protect the eyes from glare were used in China in the 12th century or earlier. Contemporary documents describe the use of such glasses by judges in Chinese courts to conceal their expressions Facials, while questioning witnesses.

James Ayscough began experimenting with tinted lenses of his glasses in the middle of the 18th century. These were not "the sunglasses "as such, Ayscough believed blue-or green-tinted glass could correct specific vision problems. Protection of the sun's rays was not a concern him.

Yellow / orange and brown sunglasses were also an element commonly prescribed for people with syphilis in the Ages 20 19 and early due to light sensitivity which was one of the symptoms of the disease.

In early 1900, the use of sunglasses started to become more widespread, particularly among the stars of silent film pioneer. It is commonly believed that this was to avoid recognition by fans, but the real reason was they often had perennial pain in the eyes of the arc lights powerful than needed, because the stocks extremely slow speed film. The stereotype persists long after improvements in film quality and the introduction of ultraviolet filters had eliminated this problem. Low-cost mass produced sunglasses were introduced to America by Sam Foster in 1929. Foster found a ready market on the beaches of Atlantic City, New Jersey, where he began selling sunglasses under the Foster Grant name of a Woolworth on the Boardwalk.

Polarized sunglasses for the first time in 1936 when Edwin H. Land began experimenting with the lenses do with his patented Polaroid filter.

Concealment of view, one has implications in face-to-face: It can hide weeping, being one of the signs of mourning, makes eye contact impossible which can be intimidating, as the stereotype of the guardian of a group of prisoners as shown in Cool Hand Luke, or can show detachment, what is considered cool in some circles. Dark sunglasses of particular shapes may be in vogue as a fashion accessory. Note that normal glasses are rarely used without a practical purpose, curiously, you can project an image of uncool nerdiness that sunglasses do not. The impact on nonverbal communication and are some cool image of the reasons why the sunglasses at night or indoors. People can also wear sunglasses to hide dilated or constricted pupils and bloodshot eyes (which revealing drug use), recent physical abuse (such as a black eye), or to compensate for increased photosensitivity. Fashion trends are another reason to use goggles sun, particularly designer sunglasses. Shutter Shades are a prime example of wear sunglasses fashion rather than functionality, due to trends in culture pop.

People with severe visual impairment, like the blind, often wear sunglasses in order to prevent others uncomfortable? No eye can see be better than seeing eyes which seem to look in the wrong direction. Those whose eyes have an abnormal appearance (for example due to cataract) or uncontrolled idiot (nystagmus) can also do so.

Sunglasses can improve visual comfort and visual clarity of protecting eyes from the glare. [3] Several types of lenses Disposable dispensed to patients after receiving mydriatic eye drops during eye examinations.

Excessive exposure to radiation ultraviolet (UV) can cause short-term and long-term eye problems such as photokeratitis, snow blindness, cataracts, pterygium, and various forms of cancer eye. [4] Medical experts often advise the public about the importance of wearing sunglasses to protect eyes from UV rays [4]. In the European Union CE mark identifies the fulfillment of quality standards glasses. In preparation for solar eclipses, health authorities often warn watching the sun with sunglasses alone.

There has not shown the correlation between high prices and increased UV protection. A 1995 study reported that "the expensive brands and polarizing sunglasses do not guarantee optimal protection against UVA. "[5] Australian Competition and Consumer Commission has also reported that" [t] he consumer can not rely on price as an indicator of quality. "[6] A survey cited below even find a pair of glasses with $ 6.95 generic protection slightly better than Salvatore Ferragamo shades. [7]

More recently, high energy visible light (HEV) has been shown to cause degeneration related macular [8] [9], and some manufacturers design to block it. Sunglasses may be especially important for children, as their ocular lenses are thought that place a lot more HEV light than adults (lenses "yellow" with age).

Some sunglasses also pass ANSI requirements Z87.1 basic impact and high impact protection. These are voluntary standards, so do not comply with all sunglasses, or manufacturers must comply. In the basic impact test, a 1 in (ball of 2.54 cm) steel is dropped on the lens of 50 cm (127). In the high-speed test, a 1 / 4 in (6.35mm) steel ball shot the lens at 150 m / s (45.72 m / s). In both tests, no part of the lens can touch the eye.

There three standards of sunglasses.

Australian Standard AS 1067. The five scores sunglasses under this standard are based on the amount of light absorbed, from 0 to 4, to provide some protection against UV radiation and sunglasses, and a high level of protection.

The U.S. standard ANSI Z80.3-1972. According to ANSI Z80.3-2001 standard, compliable the lens should have a UVB (280 to 315nm) of transmission of not more than one percent and UVA (315 to 380nm) of transmission of not more than 0.5 times the transmittance of visible light

The European standard is EN 1836:2005. The four ratings are 0 for insufficient UV protection, 1 for sufficient UV protection, 2 for good UV protection and 3 for complete UV protection.

Water sunglasses, also known as the surf sunglasses, surf goggles and water eyewear consist glasses specially adapted for use in rough waters, such as surfing. Features normally available include
a) impact test and break-resistant lenses
b) fixing strap or keep glasses in place during sports activities
buoyancy c) to prevent it from sinking should be moved to the user
cushion nose d)
e) ventilation or other method to remove the fog

Many sports use those sunglasses as surfing, windsurfing, kiteboarding, wakeboarding, kayaking, jet skiing, body boarding, water skiing.

The color of the lens can vary by style, fashion, and the end, but for general use, green, gray, yellow or brown is recommended to avoid or minimize color distortion which could be dangerous when, for example, driving a car. Gray lenses are considered neutral, because they increase contrast or distort colors. Brown and green lenses cause some minimal color distortion, but contrast-enhancing properties. Network lenses are good for the medium and low light conditions because they are good at enhancing contrast but cause a significant color distortion. Orange and yellow lenses that improving the contrast in depth perception but cause color distortion. Yellow lenses are commonly used by golfers and shooters to its contrast enhancement and the properties of depth perception. The lenses of blue or purple does not offer real benefits and are mainly cosmetic. With the introduction office computing, ergonomists can recommend tinted glasses for display operators to increase contrast. [edit] Lenses light is generally used to protect the eyes from impact, debris, dust or chemicals. Some sunglasses with interchangeable lenses optional clear lenses to protect the eyes during low light or night time activities. There are debates as to whether "blue blocking" or amber tinted lenses may have a protective effect. [11] Blue blocking sunglasses usually also block some light of other colors to work well in full sun. Some low-blue glasses are for use in the night to avoid suppression of the hormone melatonin to promote sleep. They provide sufficient light for normal activities can continue at night.

Some models have polarized Polaroid polarized lenses made of plastic sheet, to reduce glare caused by light reflected from polarizing surfaces such as water (see Brewster angle of how this works) and the polarization of diffuse sky radiation (Skylight). This can be especially useful in fisheries, as the ability to see beneath the surface of water is crucial.

A mirror coating can also be applied to the lens. This reflects coating reflects part of the light when it reaches the lens before transmission through the lens making it useful in bright conditions. These mirrored coatings can be made from any color by the manufacturer for style and fashion purposes. The color of the reflecting surface is irrelevant to the color of the lens. For example, a gray lens can be coated blue mirror, and a brown lens can have a silver lining. Sunglasses of this type are sometimes called Mirrorshades. A mirror is not heated in sunlight and prevents scattering in the bulk of the lens.

Sunglasses lenses are made of glass or plastic. Plastic lenses are typically made from acrylic, polycarbonate, CR-39 or polyurethane. Glass lenses have the best optical clarity and scratch resistance, but are heavier than plastic lenses. You can also break or break on impact. Plastic lenses are lighter but are more prone to scratches. Plastic offers more resistance to breakage of glass. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the plastic lens more common due to its low weight, high scratch resistance, and low transparency of ultraviolet and infrared radiation.

Either the above features: color, polarization, gradation, reflecting, and materials can be combined in the lens of a pair of sunglasses. Eye glasses are darker at the top of the lens, where the sky is transparent at the bottom. Corrective lenses or glasses can be made with either dark or tinted serve as sunglasses. An alternative is to use secondary corrective eyeglasses such as sunglasses oversized to fit regular glasses, clip-on lens was placed in front of the glasses, and flip-up glasses that have a dark lens that can be flipped when not in use. Photochromic lenses gradually darken in bright light.

Frames are usually made of plastic, nylon, a metal or metal alloy. Nylon frames are usually used in sports, because the weight are lightweight and flexible. They are able to flex a little and return to its original shape instead of breaking when pressure is applied to them. This flex can also help better grip vessels in the user's face. Metal frames are usually more rigid than nylon frames that can be more easily damaged when participating in sports activities but this does not mean they can not be used for such activities. Because metal frames are more rigid, some models have spring loaded hinges to help them grip the wearer's face better. The end pieces of the ear and the bridge of the nose can be textured or rubber or plastic material to hold better. The end of the ear pieces are usually curved so that wrap around the ear, however, some models have ear pieces. Oakley, for example, has the headphones directly in all vessels.

Frames can be done to keep the crystals in several different ways. There are three common styles: full frame, half the frame, and frameless. Full frame glasses that go under all eyeglasses. Half of the frames only cover half the lens, usually attached to the frames of the top of lenses and the side near the top. Frameless glasses have no frame around the lenses and the ear stems are attached directly to the lens. There are two styles frameless glasses: those that have a piece of frame material connecting the two lenses together, and they are a single lens with ear stems on each side.

Some sports-oriented sunglasses have interchangeable lens options. Lenses can be easily removed and exchanged for a different purpose, usually a lens color different. The purpose of this is to allow the user to easily change lenses when light conditions or activities change. The reason for this is because the cost of a set lens is less than the cost of a separate pair of glasses and carrying extra lenses is less bulky to carry multiple pairs of glasses. It also allows easy replacement a set of lenses that is damaged. The most common type of sunglasses with interchangeable lenses have a single lens or shield that covers both eyes. The styles used two lenses also exist, but are less common.

Bridge of the nose to support between the lens and face. Nose bridges also prevent pressure marks caused by the weight of the lens or frame on the cheeks. People with large noses may need a bridge of the nose under his sunglasses. People with the nose, half may need a low or medium nose bridge. People with small noses may need sunglasses with high nose bridges to allow clearance.

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