Variable neutral density (ND) filters are useful tools for photographers because they allow you to adjust their opacity by simply rotating them. So why not use them as tint-adjustable sunglasses? Well, that’s exactly what glasses company Ron Bell has done.
A typical photographic variable ND filter consists of two pieces of polarizing glass placed one behind the other.
Rotating the front piece to the left or right relative to the back piece will increase or decrease the tint of the filter accordingly. As the number of f-stops increases, the brightness of the light passing through the lens decreases. The maximum number depends on the filter make/model.
The titanium-frame Ronbell sunglasses simply utilize two 9-stage variable ND filters as lenses. Users can darken or brighten the lenses by simply twisting the front of each lens. Gradual markings ensure that both lenses are both set to the same opacity.
Ron Bell
The company says the glasses block more than 99% of UVA and UVB light, regardless of tint setting. Additionally, the back glass of each lens can be replaced with a custom prescription lens if desired.
And yes, photochromic transition lenses already change tint automatically. However, some people find it too slow to wear. It also won’t darken if the wearer is looking at a bright view from a shaded area (such as when driving a car on a sunny day).
Manually adjustable electrochromic sunglasses are an option, but they tend to be expensive and require batteries that need to be recharged.
Ron Bell
Lombell Variable ND Sunglasses are currently available on the company’s website at a discounted price of $89.99 for a regular pair and $99.99 for a set with prescription lenses.
Source: Rombel
