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Monday, September 12, 2011

Sunglasses

Sunglasses







Sunglasses








Sunglasses


If it's a bright, clear day outside, you may instinctively reach for your Sunglasses when you head for the door. And you probably do it without much thought about them. But you probably do think about Sunglasses when you go to buy a new pair -- whether you walk into the discount store or the Sunglass Hut at the mall, you are immediately struck by the bewildering array of choices before you! For instance, there are differences between tinted, reflective, photochromic and polarizing Sunglasses. The style of the frame and size of the lenses also make a difference. Is that $200 pair of Serengeti Sunglasses really any better than a $10 pair from the flea market?

In this article, we'll take the mystery out of Sungl­asses and help you understand what to look for when you buy a pair. We'll analyze the different styles and look at the technology behind the different lens compositions. You will also learn how light works and see why light, in certain situations, can make Sunglasses absolutely essential. You will be amazed at how complex and sophisticated a simple pair of dark glasses can be.

Then there are the imposters. You go to a discount shop or a flea market and see vendors offering Sunglasses that look exactly the same as the high-dollar brand names for a fraction of the cost. Are you really paying that much for a name or are there fundamental differences between the look-alike Sunglasses and the brand-name ones?




Sunglasses





 Sunglasses








Sunglasses

The biggest problem with cheap Sunglasses is in the way the lenses are made. Inexpensive Sunglasses have lenses made of ordinary plastic with a thin tinted coating on them. While the tint color and a similar frame design may make them look like Oakley X-Metal Romeos or Ray-Ban Predators, the actual lenses are very different. You will learn exactly how different they are, and how important the differences are, in the following sections.

Keep reading for a complete description of specific technologies like polarization, photochromic lenses, anti-reflective coatings and so on.
There are two basic ways by which we can see colors. Either an object can directly emit light waves in the frequency of the observed color (a neon light does this), or an object can absorb all other frequencies, reflecting back to your eye only the light wave, or combination of light waves, that appears as the observed color (any painted object does this). For example, to see a yellow object, either the object is directly emitting light waves in the yellow frequency, or it is absorbing the blue part of the spectrum and reflecting the red and green parts back to your eye, which perceives the combined frequencies as yellow.
When we talk about light in reference to Sunglasses, three types of light are important.

    Direct light - Direct light is light that goes straight from the light source (like the sun) to your eyes. Too much direct light can wash out the details of your surroundings and make it almost painful to try to focus your vision on anything.

    Reflected light - Reflected light, usually in the form of glare (see explanation above), is light that has bounced off a reflective object to enter your eyes. Just like direct light, strong reflected light can make it difficult to perceive the details or directly view an object. Snow, water, glass and white sand are all good reflectors.

    Ambient light - Ambient light is light that has bounced and scattered in many directions so that it is does not seem to have a specific source. A good example of ambient light is the glow in the sky around a major city. It would be very hard to identify a single source of light for that glow. Ambient light is how you are able to see when there is no direct source of light.

Good Sunglasses can eliminate the ultraviolet part of the spectrum, cut down on direct light to the point where it is comfortable and eliminate or decrease reflected light (depending on the reflecting surface).

One interesting property of light is polarization. When reflected off of certain surfaces -- such as water -- light gets polarized. Polarized Sunglasses can eliminate reflected light off of water and similar surfaces because of its polarization.

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