Sunglasses

History, The Roman emperor Nero liked to watch gladiator fights through polished gem stones. First used in China in the 12 century.  The "lenses" were flat pieces of smokey quartz, no corrective powers but protected the eyes from glare.  Judges in Chinese courts used tinted lenses to conceal facial expressions, hence the phrase, "blind justice". Introduced in America by Sam Foster in 1929, he started selling them as Foster Grants at Woolworth on the Boardwalk on the beaches of Atlantic City, and New Jersey. Polarized lens were developed in 1936 by Edwin H. Land. Wayfarers were introduced in the 1950's. Revo or revolutionary sunglass mirrored coating was developed by NASA for astronauts.

Also known as:

• Sun spectacles, by opticians.
• Spekkies in South Australia
• Sun specs, shortened version of Sun Spectacles
• Sunglasses used in Britain and North America
• Sun-Shades
• Dark glasses
• Sunnies, Australian slang
• Smoked Spectacles

Sunglasses are a visual aid, with coloured or dark lenses to screen out strong light from your eyes.  Recommended to wear on sunny days to protect your eyes from UV, that can lead to cataracts.

Sunglasses improve visual comfort and laity by protecting the eye from glare.

There is no 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 "consumers cannot rely on price as an indicator of quality."  One unscientific survey even found a $6.95 pair of generic glasses with slightly better protection than Michael Kors or Salvatore Ferragamo shades.  We tested in a UV machine a pair of our $5.00 wayfarer look alike raybans against an actual brand name Ray Ban, the $5.00 was 100% UV protected the wayfarer Ray Ban was 85%.

The food and drug administration requires all sunglasses to have UV protection.

• Green lenses minimize color distortion. Neutral, do not enhance.
• Grey,smoke, minimizes color distortion, driving, sports, golf, cycling and running and general use.
• Amber and Brown, minimizes color distortion, minimal color distortion, but contrast-enhancing. Good for sports, skiing, boating, fishing and driving.
• Green, minimal color distortion, contrast-enhancing properties
• Red, medium and lower light conditions, enhance contrast but causes color distortion
• Orange and Yellow, have the best contrast enhancement and depth perception, alters colors, used by golfers and shooters.
• Blue and purple,no benefit, cosmetic
• Clear, protect eyes from impact,debris,dust etc.,still mat offer UV protection
• Mirroredshades are sunglasses with a mirrored coating on the surface. Thick mirrored coatings sometimes crack, similar to layers of paint that is layered and thick.
• Polarized.  Polarization can happen naturally or artifically.  An example of natural polarization is when you look at a lake, the reflected glare off the surface is the light that does not make it through the water (filter) and is the reason you cannot see below the surface even when the water is clear, (without a polarized lens anyway).  Polarized sunglasses have a fixed lens that at an angle only allows vertical polarized light thru the lens.
• UV coating can eliminate UV rays, this is a clear coating and can be applied to clear lenses.
• Optical quality glass is ground and polished reduces distortion.

Tint can thru a process be put directly into the lense material when created. Or tinting can be done by putting lense in a special liquid containing tinting material that absorbs into the plastic.

Some sunglasses offer polarized lenses to reduce glare caused by reflected polarizing surfaces, like water.and snow.

Some use a degradation, the top of the glass (sky) is darker and the bottom is transparent, for looking were you are walking etc.

A mirrored coating can be applied to a lens.  The mirrored coating reflects some of the light when it hits the lens before it goes through the lens. Can be made in any color and is irrelevant to the color of the lens.  For example, a gray lens can have a blue mirror coating but you do not see the blue.

Any of the above features: color, polarization, degradation and mirroring can be combined into a set of lenses to make a pair of sunglasses, brand name or otherwise.

Mildly tinted glasses offer contrast on computer screens.

Sunglasses are made from either glass or plastic.  Plastic lenses are typically made from acrylic, polycarbonate, or CR-39.  Glass lenses have the best optical clarity and scratch resistance, but are heavier than the plastic. They can also shatter or break on impact.  Plastic lenses are lighter than glass lenses, but are more prone to scratching. 

Aviators usually a dark lense and often with a mirror coating. First created by Ray Ban in 1936 for U.S. pilots.  Now popular with all sorts of wearers.

Thank you for reading the guide on sunglasses, I hope it has been helpful to you and the choices you can make when buying them. Have a great day!