There are many different watches in the market. Find one that fits your style.
Steps
1Decide what kind of watch you want. Analog? Digital? Both?
2Choose the band. Do you want a metal band? Rubber? Polyurethane?
3Determine your price range. Under $100? Under $1000?
4Be sure that the watch can actually tell time. In other words, get one that has quartz, Swiss, or Japanese movement. Newer models have kinetic or automatic movements and store energy when the watch is worn. The movement of your wrist "winds" the watch. Be aware though that these watches should be worn daily to ensure that the "battery' is charged.
5Styling may be very important. For example if your want a sophisticated, sleek look you might want to find a sleek, thin, long silver watch. For more of the punk/rock star look, you could get one with a very wide webbing or leather band. For the classy, preppy look, a metal analog watch would be nice.
6Get a watch that is durable. You can't really tell by looking at one, but you can check its ratings by the manufacturer. Rolexes, Tag Heuers, Rado, and other well known brands are very well made. Check the manufacturer to make sure they have a reputation of good watches.
7Check for water resistance. Unless you see a marking for meters (ex. 30 meters, 100 meter, etc...) assume that it cannot be worn in water.
8If you are worried about battery life, go for digital watches, some CASIO models claim for 10 years of battery life.
Tips
-Stay within price range. Watches are easy to lose, and your investment might just go out the window.
-For the average person, a Seiko, G-Shock, Swatch, or Casio are all great values.
-If the watch which you are going purchase for everyday use and cheaper once ($20-$50), then go for such a watch for which you yourself can change batteries. This would save a lot of dollars for getting battery replaced.
-Purchase a watch with standard sized strap (10, 12, 14, 16, 20, 22 mm) as they are easily available everywhere. If the strap is too wide like 35 mm, then such straps are hard to get and are much expensive.
Warnings
-Never try to open a watch yourself. Always take it to a certified jeweler.
-Beware of counterfeit brand name watches. If it seems too cheap to be real, it probably is a fake.
-Don't buy an analog watch without markings unless you are able to read it.
-Many reputed Swiss Made watches should be bought from their offcial dealers. Buying Swiss watches online may be risky.
วันเสาร์ที่ 24 มกราคม พ.ศ. 2552
How to Pick Sunglasses
Everyone wants sunglasses that are fashionable and protect their eyes. Still, there are other considerations, and quality sunglasses can be a pretty big investment, so read these steps for some suggestions that may help you.
Steps
1Get some that offer good protection from the sun. There should be a sticker on the lens telling you if they do. Perhaps the first consideration will be that they block 100% of UV-A and UV-B (or ultraviolet A and B) light, since these wavelengths of light can damage your eyes.
2ecide whether you need polarized or non-polarized lenses. Polarized lenses decrease the amount of glare by filtering out defracted, or bent, light waves, which can be an advantage to drivers and fishermen.
3Check how much light they block. For extremely bright light situations, such as walking on snow or bright sandy beaches, darker glasses will relieve a lot of the strain on your eyes. Long term exposure to very bright light, particularly reflected off of snow, white sand, or water, can cause photokeratisis (snowblindness), a type of "sunburn" of the cornea, which is a painful, temporary form of blindness.
4Make sure the lenses offer protection for your entire retina from UV light. Narrow, small lenses may look good, but curved lenses which "wrap" slightly around your face give better protection.
5Choose sunglasses made with impact resistant glass or plastic lenses. This will decrease the chance of severe eye injuries in the event you are struck in the eye and the lens shatters.
6Pick a color which does not distort or otherwise effect your eye's ability to distinguish colors. The American volunteer eye saftey organisation, Prevent Blindness America recommends amber, grey, brown, or green lenses.
7Check the weight of your sunglasses. If you don't want to carry a heavy pair, choose some that are lightweight.
8Make sure the sunglasses fit properly. Try them on and make sure they don't pinch around your head. But make sure they are not too big. Leave them on for a few minutes and see if they start to hurt.
9Look in the mirror that should be provided. See if they suit you. You should be able to tell how they look on your face.
10Take a friend for a second opinion. Make sure it is someone who will be honest and tell you if they suit you or not.
11Think of your face shape. Not all sunglasses look great on all people. The right sunglasses will flatter your face shape:
-Aviator are good with any type, but best with an oval shape face;
-Rounded frames are great with a square face;
-Rectangular frames are great with a heart shaped face, and square frames are great with a round face.
12Try aviator shades. They are perfect for any look and give any outfit a cool retro vibe. They're timeless.
13Try oversize frames. They glam up any outfit, but be sure you look good with them on, and not cheap or like a bug.
14Find unique frames. Frames are a reflection of your personal style. Too many people wear the same frames each season, so get some different ones if you're looking for fashion. Vintage shades are awesome. Alternatively, go for a classic look and wear it year to year to save yourself some money.
15Be picky. There are loads of different sizes and styles, so keep trying them until you find the ones that are just right for you.
16Be aware that as in most purchases, price will have a bearing on quality, and because you should consider your vision priceless, it would be wise to consider investing in protection for them carefully.
17Use the same approach to buying sunglasses for children, especially since they often spend much of their time outdoors. Never buy cheap, toy sunglasses for kids, rather, purchase protective, properly fitting quality sunglasses.
Tips
1Always put your sunglasses in a hardcover case to protect them when traveling out and about; otherwise you might sit on them and mangle them.
2Think about how you will be using the sunglasses.
-If you are athletic, you may want sunglasses that will stay on when you play basketball, keep bugs out of your eyes when you ride your bike, or not steam up if you're sweating.
-Do you need them to wrap around and keep the sun out of the sides of your eyes, too?
-Some shooters and other sportsmen prefer amber or even yellow lenses for their sports, since these are purported to improve their vision, as well as protecting their eyes.
3Consider "clip on" type glasses if you wear a prescription lens eyeglass. If your prescription glasses are already 100% UV blocking material, all you will need is a lens which sufficiently blocks glare and bright light to reduce eyestrain.
Steps
1Get some that offer good protection from the sun. There should be a sticker on the lens telling you if they do. Perhaps the first consideration will be that they block 100% of UV-A and UV-B (or ultraviolet A and B) light, since these wavelengths of light can damage your eyes.
2ecide whether you need polarized or non-polarized lenses. Polarized lenses decrease the amount of glare by filtering out defracted, or bent, light waves, which can be an advantage to drivers and fishermen.
3Check how much light they block. For extremely bright light situations, such as walking on snow or bright sandy beaches, darker glasses will relieve a lot of the strain on your eyes. Long term exposure to very bright light, particularly reflected off of snow, white sand, or water, can cause photokeratisis (snowblindness), a type of "sunburn" of the cornea, which is a painful, temporary form of blindness.
4Make sure the lenses offer protection for your entire retina from UV light. Narrow, small lenses may look good, but curved lenses which "wrap" slightly around your face give better protection.
5Choose sunglasses made with impact resistant glass or plastic lenses. This will decrease the chance of severe eye injuries in the event you are struck in the eye and the lens shatters.
6Pick a color which does not distort or otherwise effect your eye's ability to distinguish colors. The American volunteer eye saftey organisation, Prevent Blindness America recommends amber, grey, brown, or green lenses.
7Check the weight of your sunglasses. If you don't want to carry a heavy pair, choose some that are lightweight.
8Make sure the sunglasses fit properly. Try them on and make sure they don't pinch around your head. But make sure they are not too big. Leave them on for a few minutes and see if they start to hurt.
9Look in the mirror that should be provided. See if they suit you. You should be able to tell how they look on your face.
10Take a friend for a second opinion. Make sure it is someone who will be honest and tell you if they suit you or not.
11Think of your face shape. Not all sunglasses look great on all people. The right sunglasses will flatter your face shape:
-Aviator are good with any type, but best with an oval shape face;
-Rounded frames are great with a square face;
-Rectangular frames are great with a heart shaped face, and square frames are great with a round face.
12Try aviator shades. They are perfect for any look and give any outfit a cool retro vibe. They're timeless.
13Try oversize frames. They glam up any outfit, but be sure you look good with them on, and not cheap or like a bug.
14Find unique frames. Frames are a reflection of your personal style. Too many people wear the same frames each season, so get some different ones if you're looking for fashion. Vintage shades are awesome. Alternatively, go for a classic look and wear it year to year to save yourself some money.
15Be picky. There are loads of different sizes and styles, so keep trying them until you find the ones that are just right for you.
16Be aware that as in most purchases, price will have a bearing on quality, and because you should consider your vision priceless, it would be wise to consider investing in protection for them carefully.
17Use the same approach to buying sunglasses for children, especially since they often spend much of their time outdoors. Never buy cheap, toy sunglasses for kids, rather, purchase protective, properly fitting quality sunglasses.
Tips
1Always put your sunglasses in a hardcover case to protect them when traveling out and about; otherwise you might sit on them and mangle them.
2Think about how you will be using the sunglasses.
-If you are athletic, you may want sunglasses that will stay on when you play basketball, keep bugs out of your eyes when you ride your bike, or not steam up if you're sweating.
-Do you need them to wrap around and keep the sun out of the sides of your eyes, too?
-Some shooters and other sportsmen prefer amber or even yellow lenses for their sports, since these are purported to improve their vision, as well as protecting their eyes.
3Consider "clip on" type glasses if you wear a prescription lens eyeglass. If your prescription glasses are already 100% UV blocking material, all you will need is a lens which sufficiently blocks glare and bright light to reduce eyestrain.
Sunglasses
Sunglasses or sun glasses are a visual aid, variously termed spectacles or glasses, which feature lenses that are coloured or darkened to prevent strong light from reaching the eyes. In the early Twentieth century they were also known as sun cheaters (or simply cheaters).
Many people find direct sunlight too bright to be comfortable. During outdoor activities, the human eye can receive more light than usual. Healthcare professionals recommend eye protection whenever outside to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have long been associated with celebrities and film actors primarily from a desire to hide or mask their identity. Since the 1940s sunglasses have been popular as a fashion accessory, especially on the beach.
History
United States Secret Service agents wearing sunglasses
PrecursorsIt is said that the Roman emperor Nero liked to watch gladiator fights with emeralds. These, however, appear to have worked rather like mirrors.Flat panes of smoky quartz which offered no corrective powers but did protect the eyes from glare were used in China in the 12th century or possibly earlier. Contemporary documents describe the use of such crystals by judges in Chinese courts to conceal their facial expressions while questioning witnesses.
James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century. These were not "sunglasses" as such; Ayscough believed blue- or green-tinted glass could correct for specific vision impairments. Protection from the sun's rays was not a concern of his.
Yellow/Amber and brown-tinted spectacles were also a commonly-prescribed item for people with syphilis in the 19th and early 20th centuries because of the sensitivity to light that was one of the symptoms of the disease.
Modern developmentsIn the early 1900s, the use of sunglasses started to become more widespread, especially among the pioneering stars of silent movies. It is commonly believed that this was to avoid recognition by fans, but the real reason was they often had perennially red eyes from the powerful arc lamps that were needed due to the extremely slow speed film stocks used[citation needed]. The stereotype persisted long after improvements in film quality and the introduction of ultraviolet filters had eliminated this problem. Inexpensive 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 name Foster Grant from a Woolworth on the Boardwalk.
Sunglasses first became polarized in 1936, when Edwin H. Land began experimenting with making lenses with his patented Polaroid filter.
Uses Paul Newman wearing sunglassesHiding one's eyes has implications in face-to-face communication: It can hide weeping, being one of the signs of mourning, makes eye contact impossible which can be intimidating, or can show detachment, which is considered cool in some circles. Darkened sunglasses of particular shapes may be in vogue as a fashion accessory. Note that normal glasses are very rarely worn without a practical purpose — curiously, they can project an image of uncool nerdiness that sunglasses do not have. The impact on nonverbal communication and the cool image are among the reasons for wearing sunglasses by night or indoors. People may also wear sunglasses to hide dilated or contracted pupils or bloodshot eyes (which would reveal drug use), recent physical abuse (such as a black eye), or to compensate for increased photosensitivity. Fashion trends are another reason for wearing sunglasses, particularly designer sunglasses. Shutter Shades are a prime example of sunglasses worn for fashion rather than functionality due to trends in pop culture.
John Major at Newlands Cricket Ground wearing sunglasses, January 2000.People with severe visual impairment, such as the blind, often wear sunglasses in order to avoid making others uncomfortable — not seeing eyes may 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 which jerk uncontrollably (nystagmus) may also do so.
Visual clarity and comfortSunglasses can improve visual comfort and visual clarity by protecting the eye from glare.Various types of disposable sunglasses are dispensed to patients after receiving mydriatic eye drops during eye examinations.
Protection Sunglasses should pass the ANSI Z87.1 requirements and offer UV protectionExcessive exposure to ultraviolet radiation (UV) can cause short-term and long-term ocular problems such as photokeratitis, snow blindness, cataracts, pterygium, and various forms of eye cancer.Medical experts often advise the public on the importance of wearing sunglasses to protect the eyes from UV. In the European Union, a CE mark identifies glasses fulfilling quality regulations. In the preparation for solar eclipses, health authorities often warn against looking at the sun through sunglasses alone.
There is no demonstrated correlation between high prices and increased UV protection. A 1995 study reported that "Expensive brands and polarizing sunglasses do not guarantee optimal UVA protection." The Australian Competition and Consumer Commission has also reported that "[c]onsumers cannot rely on price as an indicator of quality". One survey cited below even found a $6.95 pair of generic glasses with slightly better protection than Salvatore Ferragamo shades.
More recently, high-energy visible light (HEV) has been implicated as a cause of age-related macular degeneration, and some manufacturers design to block it. Sunglasses may be especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses "yellow" with age).
Some sunglasses also pass ANSI Z87.1 requirements for basic impact and high impact protection. These are voluntary standards, so not all sunglasses comply, nor are manufacturers required to comply. In the basic impact test, a 1 in (2.54 cm) steel ball is dropped on the lens from 50 in (127 cm). In the high velocity test, a 1/4 in (6.35mm) steel ball is shot at the lens at 150 ft/s (45.72 m/s). In both tests, no part of the lens can touch the eye.
StandardsThere are three sunglass standards.
The Australian Standard is AS 1067. The five sunglass ratings under this standard are based on the amount of light they absorb, 0 to 4, with “0” providing some protection from UV radiation and sunglare, and “4” a high level of protection.
The US standard is ANSI Z80.3-1972. According to the ANSI Z80.3-2001 standard, the compliable lens should have a UVB (280 to 315nm) transmittance of no more than one per cent and a UVA (315 to 380nm) transmittance of no more than 0.5 times of the visual light transmittance
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 full UV protection.
Water sunglassesWater sunglasses, also known as surfing sunglasses, surf goggles and water eyewear consist of eyewear specially adapted to be used in turbulent water, such as the surf. Features normally available includea) shatter proof & impact resistant lensesb) strap or other fixing to keep glasses in place during sporting activitiesc) buoyancy to stop them from sinking should they be displaced from the wearerd) nose cushione) vent or other method to eliminate fogging
Many sports utilize these sunglasses including surfing, windsurfing, kiteboarding, wakeboarding, kayaking, jet skiing, Bodyboarding, and water skiing.
Construction
LensThe colour of the lens can vary by style, fashion, and purpose, but for general use, green, grey, yellow, or brown is recommended to avoid or minimize color distortion which would be dangerous when, for instance, driving a car. Gray lenses are considered neutral because they do not enhance contrast or distort colors. Brown and green lenses cause some minimal color distortion, but have contrast-enhancing properties. Red lenses are good for medium and lower light conditions because they are good at enhancing contrast, but cause significant color distortion. Orange and yellow lenses have the best contrast enhancement at depth perception but cause color distortion. Yellow lenses are commonly used by golfers and shooters for its contrast enhancement and depth perception properties. Blue or purple lenses offer no real benefits and are mainly cosmetic. With the introduction of office computing, ergonomists can recommend mildly tinted glasses for display operators to increase contrast.[citation needed] Clear lenses are used typically to protect the eyes from impact, debris, dust, or chemicals. Some sunglasses with interchangeable lens have optional clear lenses to protect the eyes during low light or night time activities. Debates exist as to whether "blue blocking" or amber tinted lenses may have a protective effect. Blue blocking sunglasses typically also block some light of other colors to function well in full sunlight. Some low blue glasses are for use inside at night to avoid suppression of the sleep promoting hormone melatonin.[citation needed] They provide enough light so normal evening activities can continue.
Some models have polarized lenses, made of Polaroid polarized plastic sheet, to reduce glare caused by light reflected from polarizing surfaces such as water (see Brewster's angle for how this works) as well as by polarized diffuse sky radiation (skylight). This can be especially useful when fishing, as the ability to see beneath the surface of the water is crucial.
A mirrored coating can also be applied to the lens. This mirrored coating reflects some of the light when it hits the lens before it is transmitted through the lens making it useful in bright conditions. These mirrored coatings can be made any color by the manufacturer for styling and fashion purposes. The color of the mirrored surface is irrelevant to the color of the lens. For example, a gray lens can have a blue mirror coating, and a brown lens can have a silver coating. Sunglasses of this type are sometimes called mirrorshades. A mirror does not get hot in the sunlight and prevents scattering in the lens bulk.
Sunglass lenses are made from either 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. They can also shatter or break on impact. Plastic lenses are lighter but are more prone to scratching. Plastic offers more resistance to shattering than glass. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the most common plastic lens, due to their low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation.
Any of the above features: color, polarization, gradation, mirroring, and materials can be combined into the lens for a pair of sunglasses. Gradated glasses are darker at the top of the lens where the sky is viewed and transparent at the bottom. Corrective lenses or glasses can be manufactured with either tinting or darkened to serve as sunglasses. An alternative is to use the corrective glasses with a secondary lenses such as oversize sunglasses that fit over the regular glasses, clip-on lens that are placed in front of the glasses, and flip-up glasses which feature a dark lens that can be flipped up when not in use. Photochromic lens gradually darken in bright light.
Frames This sunglass-eyeshield uses a nylon half-frame and interchangeable lensesFrames are generally made from plastic, nylon, a metal or metal alloy. Nylon frames are usually used in sports because they are light weight and flexible. They are able to bend slightly and return to their original shape instead of breaking when pressure is applied to them. This flex can also help the glasses grip better on the wearer's face. Metal frames are usually more rigid than nylon frames thus they can be more easily damaged when participating in sporty activities, but this is not to say that they cannot 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 of the ear pieces and the bridge over the nose can be textured or have a rubber or plastic material to hold better. The end of the ear pieces are usually curved so that they wrap around the ear; however, some models have straight ear pieces. Oakley, for example, has straight ear pieces on all their glasses.
Frames can be made to hold the lenses in several different ways. There are three common styles: full frame, half frame, and frameless. Full frame glasses have the frame go all around the lenses. Half frames go around only half the lens, typically the frames attach to the top of the lenses and on the side near the top. Frameless glasses have no frame around the lenses and the ear stems are attached directly to the lenses. There are two styles of frameless glasses: those that have a piece of frame material connecting the two lenses together, and those that are a single lens with ear stems on each side.
Some sports-oriented sunglasses have interchangeable lens options. Lenses can be easily removed and swapped with a different lens, usually a different coloured lens. The purpose of this is to allow the wearer to easily change lenses when light conditions or activities change. The reason for this is because the cost of a set of lenses is less than the cost of a separate pair of glasses and carrying extra lenses is less bulky than carrying multiple pairs of glasses. It also allows easy replacement of a set of lenses if they are damaged. The most common type of sunglasses with interchangeable lenses have a single lens or shield that covers both eyes. Styles that use two lenses also exist, but are less common.
Nose BridgeNose bridges allow support between the lens and the 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 low nose bridge on their sunglasses. People with medium noses may need a low or medium nose bridge. People with small noses may need sunglasses with high nose bridges to allow clearance.
Fashion
Oversized sunglasses A girl wearing oversized sunglassesOversized sunglasses ,which were fashionable in the 1980s, are now often used for humorous purposes, and look like a pair of sunglasses that is extremely large for the face. They usually come in bright colors with colored lenses and can be purchased cheaply.
The singer Elton John would sometimes wear oversized sunglasses on stage in the mid 1970's as part of his Captain Fantastic stage act.
Over recent years however, moderately oversized sunglasses have become a fashion trend. There are many variations, such as the 'Onassis', discussed below, and Dior white sunglasses.
Onassis glassesOnassis glasses or "Jackie O's" are very large sunglasses worn by women. This style of sunglasses is said to mimic the kind most famously worn by Jacqueline Kennedy Onassis in the 1960s. The glasses continue to be popular with women, and celebrities may use these to hide from paparazzi.
MirrorshadesMain article: Mirrorshades (fashion)Mirrorshades are sunglasses with a mirrored coating on the surface. Their popularity with police officers in the United States has earned them the nickname "cop shades". The two most popular styles for these are dual lenses set in metal frames (which are often confused with Aviators), and "Wraparound" (a single, smooth, semi-circular lens that covers both eyes and much of the same area of the face covered by protective goggles, combined with a minimal plastic frame and single piece of plastic serving as a nosepiece). Wraparound sunglasses are also quite popular in the world of extreme sports.
Aviators Ray-Ban Aviator sunglasses(RB3025 004/58)Main article: Ray-Ban AviatorAviators are sunglasses with an oversized teardrop-shaped lens and thin metal frames. This design first appeared in 1936 by Ray-Ban for issue to U.S. military aviators. Their popularity with pilots, military and law enforcement personnel in the United States has never wavered. As a fashion statement, models of aviator sunglasses are often made in mirrored, colored, degregated, and wrap-around styles. In addition to pilots, Aviator-style sunglasses gained popularity with young people in the late 1960s and continued to be very popular with only a brief fall in demand during the 1990s.
WayfarersMain article: Ray-Ban WayfarerFirst introduced by Ray-Ban, the Wayfarer design popularized since the 1950s by Hollywood celebrities such as James Dean is thought to be the bestselling sunglasses design to date[citation needed].
Teashades Teashade sunglasses'Teashades' (sometimes also called "John Lennon glasses" or "Ozzy Glasses", after Ozzy Osbourne') were a type of Psychedelic art wire-rim sunglasses that were often worn, usually for purely aesthetic reasons, by members of the 1960s drug counterculture, as well as by opponents of segregation.[citation needed] Rock stars such as Mick Jagger, John Lennon, Jerry Garcia,and Ozzy Osbourne, all wore teashades. The original teashade design was made up of medium-sized, perfectly round lenses, supported by pads on the bridge of the nose and a thin wire frame. When teashades became popular in the late 1960s, they were often elaborated; lenses were elaborately colored, mirrored, and degregated, produced in excessively large sizes, and with the wire earpieces exaggerated. A uniquely-colored or darkened glass lens was usually preferred. Modern versions tend to have plastic lenses as do many other sunglasses. Teashades are rare to find in shops today however can be found at many costume websites and different countries.
The term has now fallen into disuse, although references can still be found in literature of the time. Teashades are briefly referenced during a police training seminar in Hunter S. Thompson's Fear and Loathing in Las Vegas. 'Teashades' also was used to describe glasses worn to hide the effects of marijuana (conjunctival injection) or 'bloodshot' eyes or the effects of opiates such as heroin (pupillary constriction).
The glasses worn by Seraph in the Matrix films are Teashades. Ban Mido (GetBackers) and Basara Nekki (Macross 7) are almost never seen without their purple-lensed teashades. Former professional wrestler Bret Hart is also known for wearing teashades at live and televised appearances during his wrestling career.
Tim Roth also favours teashade sunglasses.
Shutter ShadesMain article: Shutter Shades
Glacier GlassesSometimes called glacier goggles: sunglasses with leather blinders at the sides that protect the eyes by blocking the sun's rays around the edges of the lenses. Typically, these have very dark round lenses. Because they provide extra protection from bright sun and light reflected by snow and ice, they are often used when mountain climbing, or traveling across glaciers or snowfields.
Faded/ Graduated LensesThe Faded lenses refer to the fade in which sunlight is blocked from ones face. For example there will be more protection from sunlight the higher you look on the lens but the farther one looks down the less protection one gets. The fashion advantage is that one can wear them inside and not fear tripping over something and also allowing the user to see. Wearing sunglasses to nightclubs has become common in recent times, where the faded lens comes in handy. The Independent (London), has also referred to these style of sunglasses as the Murphy Lens.
Many people find direct sunlight too bright to be comfortable. During outdoor activities, the human eye can receive more light than usual. Healthcare professionals recommend eye protection whenever outside to protect the eyes from ultraviolet radiation, which can lead to the development of a cataract. Sunglasses have long been associated with celebrities and film actors primarily from a desire to hide or mask their identity. Since the 1940s sunglasses have been popular as a fashion accessory, especially on the beach.
History
United States Secret Service agents wearing sunglasses
PrecursorsIt is said that the Roman emperor Nero liked to watch gladiator fights with emeralds. These, however, appear to have worked rather like mirrors.Flat panes of smoky quartz which offered no corrective powers but did protect the eyes from glare were used in China in the 12th century or possibly earlier. Contemporary documents describe the use of such crystals by judges in Chinese courts to conceal their facial expressions while questioning witnesses.
James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century. These were not "sunglasses" as such; Ayscough believed blue- or green-tinted glass could correct for specific vision impairments. Protection from the sun's rays was not a concern of his.
Yellow/Amber and brown-tinted spectacles were also a commonly-prescribed item for people with syphilis in the 19th and early 20th centuries because of the sensitivity to light that was one of the symptoms of the disease.
Modern developmentsIn the early 1900s, the use of sunglasses started to become more widespread, especially among the pioneering stars of silent movies. It is commonly believed that this was to avoid recognition by fans, but the real reason was they often had perennially red eyes from the powerful arc lamps that were needed due to the extremely slow speed film stocks used[citation needed]. The stereotype persisted long after improvements in film quality and the introduction of ultraviolet filters had eliminated this problem. Inexpensive 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 name Foster Grant from a Woolworth on the Boardwalk.
Sunglasses first became polarized in 1936, when Edwin H. Land began experimenting with making lenses with his patented Polaroid filter.
Uses Paul Newman wearing sunglassesHiding one's eyes has implications in face-to-face communication: It can hide weeping, being one of the signs of mourning, makes eye contact impossible which can be intimidating, or can show detachment, which is considered cool in some circles. Darkened sunglasses of particular shapes may be in vogue as a fashion accessory. Note that normal glasses are very rarely worn without a practical purpose — curiously, they can project an image of uncool nerdiness that sunglasses do not have. The impact on nonverbal communication and the cool image are among the reasons for wearing sunglasses by night or indoors. People may also wear sunglasses to hide dilated or contracted pupils or bloodshot eyes (which would reveal drug use), recent physical abuse (such as a black eye), or to compensate for increased photosensitivity. Fashion trends are another reason for wearing sunglasses, particularly designer sunglasses. Shutter Shades are a prime example of sunglasses worn for fashion rather than functionality due to trends in pop culture.
John Major at Newlands Cricket Ground wearing sunglasses, January 2000.People with severe visual impairment, such as the blind, often wear sunglasses in order to avoid making others uncomfortable — not seeing eyes may 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 which jerk uncontrollably (nystagmus) may also do so.
Visual clarity and comfortSunglasses can improve visual comfort and visual clarity by protecting the eye from glare.Various types of disposable sunglasses are dispensed to patients after receiving mydriatic eye drops during eye examinations.
Protection Sunglasses should pass the ANSI Z87.1 requirements and offer UV protectionExcessive exposure to ultraviolet radiation (UV) can cause short-term and long-term ocular problems such as photokeratitis, snow blindness, cataracts, pterygium, and various forms of eye cancer.Medical experts often advise the public on the importance of wearing sunglasses to protect the eyes from UV. In the European Union, a CE mark identifies glasses fulfilling quality regulations. In the preparation for solar eclipses, health authorities often warn against looking at the sun through sunglasses alone.
There is no demonstrated correlation between high prices and increased UV protection. A 1995 study reported that "Expensive brands and polarizing sunglasses do not guarantee optimal UVA protection." The Australian Competition and Consumer Commission has also reported that "[c]onsumers cannot rely on price as an indicator of quality". One survey cited below even found a $6.95 pair of generic glasses with slightly better protection than Salvatore Ferragamo shades.
More recently, high-energy visible light (HEV) has been implicated as a cause of age-related macular degeneration, and some manufacturers design to block it. Sunglasses may be especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses "yellow" with age).
Some sunglasses also pass ANSI Z87.1 requirements for basic impact and high impact protection. These are voluntary standards, so not all sunglasses comply, nor are manufacturers required to comply. In the basic impact test, a 1 in (2.54 cm) steel ball is dropped on the lens from 50 in (127 cm). In the high velocity test, a 1/4 in (6.35mm) steel ball is shot at the lens at 150 ft/s (45.72 m/s). In both tests, no part of the lens can touch the eye.
StandardsThere are three sunglass standards.
The Australian Standard is AS 1067. The five sunglass ratings under this standard are based on the amount of light they absorb, 0 to 4, with “0” providing some protection from UV radiation and sunglare, and “4” a high level of protection.
The US standard is ANSI Z80.3-1972. According to the ANSI Z80.3-2001 standard, the compliable lens should have a UVB (280 to 315nm) transmittance of no more than one per cent and a UVA (315 to 380nm) transmittance of no more than 0.5 times of the visual light transmittance
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 full UV protection.
Water sunglassesWater sunglasses, also known as surfing sunglasses, surf goggles and water eyewear consist of eyewear specially adapted to be used in turbulent water, such as the surf. Features normally available includea) shatter proof & impact resistant lensesb) strap or other fixing to keep glasses in place during sporting activitiesc) buoyancy to stop them from sinking should they be displaced from the wearerd) nose cushione) vent or other method to eliminate fogging
Many sports utilize these sunglasses including surfing, windsurfing, kiteboarding, wakeboarding, kayaking, jet skiing, Bodyboarding, and water skiing.
Construction
LensThe colour of the lens can vary by style, fashion, and purpose, but for general use, green, grey, yellow, or brown is recommended to avoid or minimize color distortion which would be dangerous when, for instance, driving a car. Gray lenses are considered neutral because they do not enhance contrast or distort colors. Brown and green lenses cause some minimal color distortion, but have contrast-enhancing properties. Red lenses are good for medium and lower light conditions because they are good at enhancing contrast, but cause significant color distortion. Orange and yellow lenses have the best contrast enhancement at depth perception but cause color distortion. Yellow lenses are commonly used by golfers and shooters for its contrast enhancement and depth perception properties. Blue or purple lenses offer no real benefits and are mainly cosmetic. With the introduction of office computing, ergonomists can recommend mildly tinted glasses for display operators to increase contrast.[citation needed] Clear lenses are used typically to protect the eyes from impact, debris, dust, or chemicals. Some sunglasses with interchangeable lens have optional clear lenses to protect the eyes during low light or night time activities. Debates exist as to whether "blue blocking" or amber tinted lenses may have a protective effect. Blue blocking sunglasses typically also block some light of other colors to function well in full sunlight. Some low blue glasses are for use inside at night to avoid suppression of the sleep promoting hormone melatonin.[citation needed] They provide enough light so normal evening activities can continue.
Some models have polarized lenses, made of Polaroid polarized plastic sheet, to reduce glare caused by light reflected from polarizing surfaces such as water (see Brewster's angle for how this works) as well as by polarized diffuse sky radiation (skylight). This can be especially useful when fishing, as the ability to see beneath the surface of the water is crucial.
A mirrored coating can also be applied to the lens. This mirrored coating reflects some of the light when it hits the lens before it is transmitted through the lens making it useful in bright conditions. These mirrored coatings can be made any color by the manufacturer for styling and fashion purposes. The color of the mirrored surface is irrelevant to the color of the lens. For example, a gray lens can have a blue mirror coating, and a brown lens can have a silver coating. Sunglasses of this type are sometimes called mirrorshades. A mirror does not get hot in the sunlight and prevents scattering in the lens bulk.
Sunglass lenses are made from either 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. They can also shatter or break on impact. Plastic lenses are lighter but are more prone to scratching. Plastic offers more resistance to shattering than glass. Polycarbonate plastic lenses are the lightest, and are also almost shatterproof, making them good for impact protection. CR-39 is the most common plastic lens, due to their low weight, high scratch resistance, and low transparency for ultraviolet and infrared radiation.
Any of the above features: color, polarization, gradation, mirroring, and materials can be combined into the lens for a pair of sunglasses. Gradated glasses are darker at the top of the lens where the sky is viewed and transparent at the bottom. Corrective lenses or glasses can be manufactured with either tinting or darkened to serve as sunglasses. An alternative is to use the corrective glasses with a secondary lenses such as oversize sunglasses that fit over the regular glasses, clip-on lens that are placed in front of the glasses, and flip-up glasses which feature a dark lens that can be flipped up when not in use. Photochromic lens gradually darken in bright light.
Frames This sunglass-eyeshield uses a nylon half-frame and interchangeable lensesFrames are generally made from plastic, nylon, a metal or metal alloy. Nylon frames are usually used in sports because they are light weight and flexible. They are able to bend slightly and return to their original shape instead of breaking when pressure is applied to them. This flex can also help the glasses grip better on the wearer's face. Metal frames are usually more rigid than nylon frames thus they can be more easily damaged when participating in sporty activities, but this is not to say that they cannot 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 of the ear pieces and the bridge over the nose can be textured or have a rubber or plastic material to hold better. The end of the ear pieces are usually curved so that they wrap around the ear; however, some models have straight ear pieces. Oakley, for example, has straight ear pieces on all their glasses.
Frames can be made to hold the lenses in several different ways. There are three common styles: full frame, half frame, and frameless. Full frame glasses have the frame go all around the lenses. Half frames go around only half the lens, typically the frames attach to the top of the lenses and on the side near the top. Frameless glasses have no frame around the lenses and the ear stems are attached directly to the lenses. There are two styles of frameless glasses: those that have a piece of frame material connecting the two lenses together, and those that are a single lens with ear stems on each side.
Some sports-oriented sunglasses have interchangeable lens options. Lenses can be easily removed and swapped with a different lens, usually a different coloured lens. The purpose of this is to allow the wearer to easily change lenses when light conditions or activities change. The reason for this is because the cost of a set of lenses is less than the cost of a separate pair of glasses and carrying extra lenses is less bulky than carrying multiple pairs of glasses. It also allows easy replacement of a set of lenses if they are damaged. The most common type of sunglasses with interchangeable lenses have a single lens or shield that covers both eyes. Styles that use two lenses also exist, but are less common.
Nose BridgeNose bridges allow support between the lens and the 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 low nose bridge on their sunglasses. People with medium noses may need a low or medium nose bridge. People with small noses may need sunglasses with high nose bridges to allow clearance.
Fashion
Oversized sunglasses A girl wearing oversized sunglassesOversized sunglasses ,which were fashionable in the 1980s, are now often used for humorous purposes, and look like a pair of sunglasses that is extremely large for the face. They usually come in bright colors with colored lenses and can be purchased cheaply.
The singer Elton John would sometimes wear oversized sunglasses on stage in the mid 1970's as part of his Captain Fantastic stage act.
Over recent years however, moderately oversized sunglasses have become a fashion trend. There are many variations, such as the 'Onassis', discussed below, and Dior white sunglasses.
Onassis glassesOnassis glasses or "Jackie O's" are very large sunglasses worn by women. This style of sunglasses is said to mimic the kind most famously worn by Jacqueline Kennedy Onassis in the 1960s. The glasses continue to be popular with women, and celebrities may use these to hide from paparazzi.
MirrorshadesMain article: Mirrorshades (fashion)Mirrorshades are sunglasses with a mirrored coating on the surface. Their popularity with police officers in the United States has earned them the nickname "cop shades". The two most popular styles for these are dual lenses set in metal frames (which are often confused with Aviators), and "Wraparound" (a single, smooth, semi-circular lens that covers both eyes and much of the same area of the face covered by protective goggles, combined with a minimal plastic frame and single piece of plastic serving as a nosepiece). Wraparound sunglasses are also quite popular in the world of extreme sports.
Aviators Ray-Ban Aviator sunglasses(RB3025 004/58)Main article: Ray-Ban AviatorAviators are sunglasses with an oversized teardrop-shaped lens and thin metal frames. This design first appeared in 1936 by Ray-Ban for issue to U.S. military aviators. Their popularity with pilots, military and law enforcement personnel in the United States has never wavered. As a fashion statement, models of aviator sunglasses are often made in mirrored, colored, degregated, and wrap-around styles. In addition to pilots, Aviator-style sunglasses gained popularity with young people in the late 1960s and continued to be very popular with only a brief fall in demand during the 1990s.
WayfarersMain article: Ray-Ban WayfarerFirst introduced by Ray-Ban, the Wayfarer design popularized since the 1950s by Hollywood celebrities such as James Dean is thought to be the bestselling sunglasses design to date[citation needed].
Teashades Teashade sunglasses'Teashades' (sometimes also called "John Lennon glasses" or "Ozzy Glasses", after Ozzy Osbourne') were a type of Psychedelic art wire-rim sunglasses that were often worn, usually for purely aesthetic reasons, by members of the 1960s drug counterculture, as well as by opponents of segregation.[citation needed] Rock stars such as Mick Jagger, John Lennon, Jerry Garcia,and Ozzy Osbourne, all wore teashades. The original teashade design was made up of medium-sized, perfectly round lenses, supported by pads on the bridge of the nose and a thin wire frame. When teashades became popular in the late 1960s, they were often elaborated; lenses were elaborately colored, mirrored, and degregated, produced in excessively large sizes, and with the wire earpieces exaggerated. A uniquely-colored or darkened glass lens was usually preferred. Modern versions tend to have plastic lenses as do many other sunglasses. Teashades are rare to find in shops today however can be found at many costume websites and different countries.
The term has now fallen into disuse, although references can still be found in literature of the time. Teashades are briefly referenced during a police training seminar in Hunter S. Thompson's Fear and Loathing in Las Vegas. 'Teashades' also was used to describe glasses worn to hide the effects of marijuana (conjunctival injection) or 'bloodshot' eyes or the effects of opiates such as heroin (pupillary constriction).
The glasses worn by Seraph in the Matrix films are Teashades. Ban Mido (GetBackers) and Basara Nekki (Macross 7) are almost never seen without their purple-lensed teashades. Former professional wrestler Bret Hart is also known for wearing teashades at live and televised appearances during his wrestling career.
Tim Roth also favours teashade sunglasses.
Shutter ShadesMain article: Shutter Shades
Glacier GlassesSometimes called glacier goggles: sunglasses with leather blinders at the sides that protect the eyes by blocking the sun's rays around the edges of the lenses. Typically, these have very dark round lenses. Because they provide extra protection from bright sun and light reflected by snow and ice, they are often used when mountain climbing, or traveling across glaciers or snowfields.
Faded/ Graduated LensesThe Faded lenses refer to the fade in which sunlight is blocked from ones face. For example there will be more protection from sunlight the higher you look on the lens but the farther one looks down the less protection one gets. The fashion advantage is that one can wear them inside and not fear tripping over something and also allowing the user to see. Wearing sunglasses to nightclubs has become common in recent times, where the faded lens comes in handy. The Independent (London), has also referred to these style of sunglasses as the Murphy Lens.
Rolex
The Rolex Watch Company improved Harwood's design in 1930 and used it as the basis for the Rolex Oyster Perpetual, in which the centrally mounted semi-circular weight could rotate through a full 360° rather than the 300° of the 'bumper' winder. Rolex's version also increased the amount of energy stored in the mainspring, allowing it to run autonomously for up to 35 hours.
Automatic Watch
An automatic or self-winding watch is a mechanical watch, whose mainspring is wound automatically by the natural motion of the wearer's arm, to make it unnecessary to manually wind the watch. Most mechanical watches sold today are self-winding.
How it works
To accomplish this, the watch contains a semicircular 'rotor', an eccentric weight that turns on a pivot, within the watch case. The normal movements of the user's arm and wrist cause the rotor to pivot back-and-forth on its staff, which is attached to a ratcheted winding mechanism. The motion of the wearer's arm is thereby translated into the circular motion of the rotor that, through a series of reverser and reducing gears, eventually winds the mainspring. Modern self-winding mechanisms have two ratchets and wind the mainspring during both clockwise and counterclockwise rotor motions.
The fully-wound mainspring in a typical watch can store enough energy reserve for roughly two days, allowing automatics to keep running through the night while off the wrist. Usually automatic watches can also be wound manually by turning the crown, so the watch can be kept running when not worn, and in case the wearer's wrist motions are not sufficient to keep it wound automatically.
Preventing overwindingA problem that had to be solved with self-winding mechanisms is that they continued working even after the mainspring was fully wound up, putting excessive tension on the mainspring. This causes a problem called 'knocking' or 'banking'. The excessive drive force applied to the watch movement gear train made the balance wheel rotate with too much amplitude, that is too far in each direction, causing the impulse pin to hit the back of the pallet fork horns. This made the watch run fast, and could break the impulse pin. To prevent this, a slipping clutch device is used on the mainspring so it cannot be overwound.
The slipping spring or 'bridle'The 'slipping mainspring' device was patented by Adrien Philippe, founder of Patek Philippe on June 16, 1863, long before self-winding watches. It was originally invented to allow simultaneous winding of two mainspring barrels. In an ordinary watch mainspring barrel, the outer end of the spiral mainspring is attached to the inside of the barrel. In the slipping barrel, the mainspring is attached to a circular steel expansion spring, often called the 'bridle', which presses against the inside wall of the barrel, which has serrations or notches to hold it.
As long as the mainspring is less than fully wound, the bridle holds the mainspring by friction to the barrel wall, allowing the mainspring to be wound. When the mainspring reaches full wind, its force is stronger than the bridle spring, and further winding pulls the bridle loose from the notches and it simply slides along the wall, preventing the mainspring from being wound further. The bridle must grip the barrel wall with just the right force to allow the mainspring to wind fully but not overwind. If it grips too loosely, the mainspring will begin to slip before it is fully wound, a defect known as 'mainspring creep' which results in a shortened reserve power time.
A further advantage of this device is that the mainspring can't be broken by overzealous manual winding. It is often referred to misleadingly in watch company terminology as an 'unbreakable mainspring'.
Automatic quartz or kinetic movementMore recently, electronic quartz watches that are powered by arm movement have been developed. A weighted rotor turns a tiny electrical generator, charging a rechargeable battery or capacitor which powers the quartz movement. This automatic quartz arrangement provides the accuracy of quartz without the need to replace the battery or capacitor until it reaches the end of its life, which may be decades.
The watch winderFor people who do not wear their automatic watch every day, watch winders are available to store automatic watches and keep them wound. This is particularly advantageous if the watch has complex complications, like perpetual calendars or moon phases. A watch winder is a device that can hold one or more watches and moves them in circular patterns to approximate the human motion that otherwise keeps the self-winding mechanism working. A mechanical watch should be kept wound and running as much as possible to prevent its lubricants from congealing over time, which diminishes accuracy. A full service (which involves disassembly, cleaning and re-lubrication) should be performed at least every five years to keep the movement as accurate as possible.
History
Perrelet
Perrelet working on a watchThe Swiss watchmaker Abraham-Louis Perrelet invented a self-winding mechanism in 1770 for pocket watches. It worked on the same principle as a modern pedometer, and was designed to wind as the owner walked, using an oscillating weight inside the large watch that moved up and down. The Geneva Society of Arts reported in 1776 that fifteen minutes walking was necessary to wind the watch sufficiently for eight days, and the following year reported that it was selling well.
Breguet
Perrelet sold some of his watches to a contemporary watch making luminary, Abraham-Louis Breguet around 1780 who improved upon the mechanism in his own version of the design, calling his watches "perpetuelles" the French word for perpetual. They did not work reliably and Breguet stopped producing them around 1800.
'Bumper' wristwatches: 1923
Self winding mechanisms were more successful in wristwatches because the rotor could operate every time that the owner moved his or her arm. The first version did not appear until after World War 1, when wristwatches became popular. It was invented by a watch repairer from the Isle of Man named John Harwood in 1923, who took out a UK patent with his financial backer, Harry Cutts, on 7 July 1923, and a corresponding Swiss patent on 16 October 1923. The Harwood system used a pivoting weight which swung as the wearer moved, and which in turn wound the mainspring. The ratchet mechanism only wound the mainspring when moving in one direction. The weight didn't rotate a full 360°; spring bumpers limited its swing to about 180°, to encourage a back and forth motion. This early type of self-winding mechanism is now referred to as a 'hammer' or 'bumper'.
When fully wound, the watch would run for 12 hours autonomously. It did not have a conventional stem winder, so the hands were moved manually by rotating a bezel around the face of the watch. The watches were first produced with the help of Swiss watch manufacturer Fortis and went on sale in 1928. 30,000 were made before the Harwood Self-Winding Watch Company collapsed in 1931 as a result of the Great Depression. 'Bumper' watches were the first commercially successful automatic watches; they were made by several high grade watch manufacturers during the 1930s and 1940s.
Rolex
The Rolex Watch Company improved Harwood's design in 1930 and used it as the basis for the Rolex Oyster Perpetual, in which the centrally mounted semi-circular weight could rotate through a full 360° rather than the 300° of the 'bumper' winder. Rolex's version also increased the amount of energy stored in the mainspring, allowing it to run autonomously for up to 35 hours.
By the 1960s, automatic winding became standard in quality mechanical watches. Because the weighted rotor needed in an automatic watch takes up a lot of room in the case, increasing the thickness of the watch, some high end watch companies, such as Patek Philippe, continue to design manually wound watches, which can achieve a case thickness as low as 1.77 millimeters.
How it works
To accomplish this, the watch contains a semicircular 'rotor', an eccentric weight that turns on a pivot, within the watch case. The normal movements of the user's arm and wrist cause the rotor to pivot back-and-forth on its staff, which is attached to a ratcheted winding mechanism. The motion of the wearer's arm is thereby translated into the circular motion of the rotor that, through a series of reverser and reducing gears, eventually winds the mainspring. Modern self-winding mechanisms have two ratchets and wind the mainspring during both clockwise and counterclockwise rotor motions.
The fully-wound mainspring in a typical watch can store enough energy reserve for roughly two days, allowing automatics to keep running through the night while off the wrist. Usually automatic watches can also be wound manually by turning the crown, so the watch can be kept running when not worn, and in case the wearer's wrist motions are not sufficient to keep it wound automatically.
Preventing overwindingA problem that had to be solved with self-winding mechanisms is that they continued working even after the mainspring was fully wound up, putting excessive tension on the mainspring. This causes a problem called 'knocking' or 'banking'. The excessive drive force applied to the watch movement gear train made the balance wheel rotate with too much amplitude, that is too far in each direction, causing the impulse pin to hit the back of the pallet fork horns. This made the watch run fast, and could break the impulse pin. To prevent this, a slipping clutch device is used on the mainspring so it cannot be overwound.
The slipping spring or 'bridle'The 'slipping mainspring' device was patented by Adrien Philippe, founder of Patek Philippe on June 16, 1863, long before self-winding watches. It was originally invented to allow simultaneous winding of two mainspring barrels. In an ordinary watch mainspring barrel, the outer end of the spiral mainspring is attached to the inside of the barrel. In the slipping barrel, the mainspring is attached to a circular steel expansion spring, often called the 'bridle', which presses against the inside wall of the barrel, which has serrations or notches to hold it.
As long as the mainspring is less than fully wound, the bridle holds the mainspring by friction to the barrel wall, allowing the mainspring to be wound. When the mainspring reaches full wind, its force is stronger than the bridle spring, and further winding pulls the bridle loose from the notches and it simply slides along the wall, preventing the mainspring from being wound further. The bridle must grip the barrel wall with just the right force to allow the mainspring to wind fully but not overwind. If it grips too loosely, the mainspring will begin to slip before it is fully wound, a defect known as 'mainspring creep' which results in a shortened reserve power time.
A further advantage of this device is that the mainspring can't be broken by overzealous manual winding. It is often referred to misleadingly in watch company terminology as an 'unbreakable mainspring'.
Automatic quartz or kinetic movementMore recently, electronic quartz watches that are powered by arm movement have been developed. A weighted rotor turns a tiny electrical generator, charging a rechargeable battery or capacitor which powers the quartz movement. This automatic quartz arrangement provides the accuracy of quartz without the need to replace the battery or capacitor until it reaches the end of its life, which may be decades.
The watch winderFor people who do not wear their automatic watch every day, watch winders are available to store automatic watches and keep them wound. This is particularly advantageous if the watch has complex complications, like perpetual calendars or moon phases. A watch winder is a device that can hold one or more watches and moves them in circular patterns to approximate the human motion that otherwise keeps the self-winding mechanism working. A mechanical watch should be kept wound and running as much as possible to prevent its lubricants from congealing over time, which diminishes accuracy. A full service (which involves disassembly, cleaning and re-lubrication) should be performed at least every five years to keep the movement as accurate as possible.
History
Perrelet
Perrelet working on a watchThe Swiss watchmaker Abraham-Louis Perrelet invented a self-winding mechanism in 1770 for pocket watches. It worked on the same principle as a modern pedometer, and was designed to wind as the owner walked, using an oscillating weight inside the large watch that moved up and down. The Geneva Society of Arts reported in 1776 that fifteen minutes walking was necessary to wind the watch sufficiently for eight days, and the following year reported that it was selling well.
Breguet
Perrelet sold some of his watches to a contemporary watch making luminary, Abraham-Louis Breguet around 1780 who improved upon the mechanism in his own version of the design, calling his watches "perpetuelles" the French word for perpetual. They did not work reliably and Breguet stopped producing them around 1800.
'Bumper' wristwatches: 1923
Self winding mechanisms were more successful in wristwatches because the rotor could operate every time that the owner moved his or her arm. The first version did not appear until after World War 1, when wristwatches became popular. It was invented by a watch repairer from the Isle of Man named John Harwood in 1923, who took out a UK patent with his financial backer, Harry Cutts, on 7 July 1923, and a corresponding Swiss patent on 16 October 1923. The Harwood system used a pivoting weight which swung as the wearer moved, and which in turn wound the mainspring. The ratchet mechanism only wound the mainspring when moving in one direction. The weight didn't rotate a full 360°; spring bumpers limited its swing to about 180°, to encourage a back and forth motion. This early type of self-winding mechanism is now referred to as a 'hammer' or 'bumper'.
When fully wound, the watch would run for 12 hours autonomously. It did not have a conventional stem winder, so the hands were moved manually by rotating a bezel around the face of the watch. The watches were first produced with the help of Swiss watch manufacturer Fortis and went on sale in 1928. 30,000 were made before the Harwood Self-Winding Watch Company collapsed in 1931 as a result of the Great Depression. 'Bumper' watches were the first commercially successful automatic watches; they were made by several high grade watch manufacturers during the 1930s and 1940s.
Rolex
The Rolex Watch Company improved Harwood's design in 1930 and used it as the basis for the Rolex Oyster Perpetual, in which the centrally mounted semi-circular weight could rotate through a full 360° rather than the 300° of the 'bumper' winder. Rolex's version also increased the amount of energy stored in the mainspring, allowing it to run autonomously for up to 35 hours.
By the 1960s, automatic winding became standard in quality mechanical watches. Because the weighted rotor needed in an automatic watch takes up a lot of room in the case, increasing the thickness of the watch, some high end watch companies, such as Patek Philippe, continue to design manually wound watches, which can achieve a case thickness as low as 1.77 millimeters.
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