Adjustable filters are handy tools for photographers, in that their opacity can be adjusted simply by rotating them. So, why not use the same idea for sunglasses?
Well, that's exactly what eyewear company Lombell has done with its smart new adjustable shades. So you can tune the opacity to suit the brightness of the sun.
A typical photographic variable ND filter consists of two pieces of polarized glass, arranged one in front of the other. When the front piece is rotated to the left or right relative to the back piece, the filter's tint increases or decreases accordingly. As it increases, the brightness of the light passing through into the lens is reduced by an increasing number of f-stops – the maximum number depends on the make/model of the filter.
The titanium-frame Lombell sunglasses simply take two 9-stop variable ND filters and utilize them as their lenses. Users just twist the front piece of each lens to make it darker or brighter. Gradated markings ensure that the two lenses both get set to the same opacity.
The glasses, Lombell claims, block over 99 percent of UVA and UVB light regardless of the tint setting. What's more, the back piece of glass in each lens can be replaced with a custom prescription lens if needed.
The Lombell variable ND sunglasses are available via the company website, at a currently discounted price of US$89.99 for a regular pair or $99.99 for a set with prescription lenses.