Sunglasses

The choice is up to you cause they come in two classes:Rhinestone shades or cheap sunglasses - ZZ Top

Fit


It is important that you find a pair of sunglasses that fits you comfortably. Look for frames that grab you securely and fit snugly on your nose and ears, but that don't pinch or rub. Make sure the weight of your sunglasses is evenly distributed between your ears and nose.


UV


When purchasing sunglasses ultraviolt (UV) protection should be the primary decision. As well as UV protevtion, high performance sunglasses should offer enhanced visual quality through exceptional light filtration and uniform lens color, and they should not lose their color or ability to filter light over the life of the sunwear.


Protection from harmful UV rays is vital to long-term eye health. UV radiation in sunlight is commonly divided into UVA and UVB, and your sunglasses should block both forms. Sunglasses should block 99% to 100% of UV, or are rated UV 400. UV 400 protection lenses are designed to block 100% blue light with wavelengths up to 400 nanometers. Hard resin (or standard plastic) lenses block most UV light, but adding a UV blocking dye can boost UV protection to 100%. New technology plastic lens materials like polycarbonate and Trivex materials have 100% UV protection built-in.


Design


Sunglasses today are designed to be used in a wide range of activities. When considering the proper pair of sunglasses the kind of activities planned should be an important factor in your decision. Will they be used in low-light conditions, at high-altitude, near or on the water, all conditions that should be planned for. Sunglasses are also made to provide different levels of protection. The material sunglass lenses are made out of will affect their cost, clarity, weight, and durability.


Lens Material

  • Glass - Glass lenses provide excellent clarity for lens materials. However, they are heavier and more expensive than other options.
  • Polycarbonate -Polycarbonate lenses are very affordable and amazingly clear. The combination of impact resistance, light weight and low bulk make them an excellent choice for a wide variety of activities.
  • Trivex - Trivex like polycarbonate lenses, lenses made of Trivex are thin, lightweight and much more impact-resistant than regular plastic or glass lenses, with the advantage of crisper optics.
  • Acrylic - Acrylic is a tough, extremely affordable plastic alternative to polycarbonate. It provides less optical clarity and durability than the options listed above, and can cause some image distortion.

Frame Material

  • Metal - Metal frames are easy to adjust to your specific face and head shape.
  • Nylon - Nylon frames are not adjustable (unless they have an adjustable wire core), but they tend to be more durable and less expensive.
  • Acetate - Acetate is a form of plastic very similar to nylon in weight, feel and function.

Light Transmission


The amount of light that reaches the eyes is a result of several factors, the color and thickness of the lenses, the material they're made of and the coating applied to them. Most all-purpose sunglasses let in between 15% and 25% of visible light. Protection in that range should be a minimum for everyday uses and basic recreational activities.


Speciality Sunglasses (Speciality sunglasses don't necessarily block UV radiation.)

  • Polarized Lenses - Polarized lenses have a special filter built into them that blocks flat, reflected light (off of snow, water, glass). These filters also optimize true colors, giving you a clearer view of the world around you no matter how bright or hazy it gets. Polarized lenses reduce contrast between objects, which can be a hindrance in low-light conditions or fast-paced activities like skiing or driving.
  • Glacier Lenses - designed specifically to protect your eyes from the intense light at high altitudes these glasses allow only 4% to 10% of light in. Most glacier glasses also have side shields to block or limit light from entering in from the sides. These glasses are a poor choice for low-light activities.
  • Photochromic Lenses - These lenses automatically adjust to changing light conditions. These lenses get darker when things get brighter outside, and lighter when conditions get darker.

Lens Color & Tinting


Sunglass lenses are tinted to cut down on overall brightness, lens color greatly affects the filtration of light through the lens. Tinting has been developed to create a fixed tint that has a depth of 0.9 mm from the front surface of the lens. This process allows for deeper dye penetration than surface tinting so the color and light filtration do not change over the life of the lens. It is important to consider different tint colors have different effects on your vision. The specific lens color you choose will affect:


  • How much visible light reaches your eyes
  • How well you see other colors
  • How well you see contrasts

For Example:



Canebrake13