The CTRL XC is designed to react to changing light conditions, with light transmittance between S1 and S3. The change takes place in 0.1 seconds – a lot quicker than standard photochromatics – and unlike photochromatic lenses is also configurable by the wearer.
Light transmittance for glasses is graded between S0 which is completely clear and S4 which is suitable for traversing polar ice caps in the summer, so the CTRL XCs cover the majority of likely uses.
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The technology is based on that developed for use by US Special Forces. The sunglasses will switch automatically between two different transmittance levels or can also be controlled manually. In automatic mode, a built-in sensor determines when to switch. There’s the option to adjust the threshold light level at which they switch between tint levels.
There’s a video here.
CTRL says that the sunglasses have a 70 hour battery life and they are recharged via a USB cable. They are also anti-fog treated and can fit prescription lenses.
The original CTRL sunglasses are already in production. They have a half frame, but the new XC model is designed with a full frame and additional features.
Production of the XC sunglasses is being funded via Indiegogo, with pledges between $150 and $175 securing a pair. Or for $675 you can get your hands on five pairs. But you’d better hurry as funding (and the summer) ends in four day’s time.