sunglasses for mountaineering

The essential thing to try to find in a high-altitude snow lens is that it has a classification four ranking-- which implies it will block approximately 90% of visible light, Yardley says. Lens categories measure the level of darkness: zero is absolutely clear and 4 is the darkest you can buy. Many everyday-use sunglasses are category 3, which obstruct approximately 81-87% of noticeable light. This is excellent for driving and walking on a bright day, but you require classification 4 lenses when you are dealing with the brightness of snow and ice all day at elevation.
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