What are photochromic lenses and how do they work?

Photochromic lenses or transitions are those that change their transparency depending on the brightness of the light. The lighter it is around, the darker the lens becomes, and vice versa: the weaker the illumination, the more transparent it is. One mask or pair of glasses can replace several others, which gives its owner the opportunity to save money. Photochromic lenses allow people with poor eyesight to use the same pair of corrective glasses outdoors and indoors. In a sports environment, the ability of the lens to smoothly change the dimming is also in demand, since athletes must always protect their eyes.

Sounds almost unbelievable, right? Today we will analyze all the nuances of these lenses, and tell you a little about our own.

How do photochromic lenses work?

Photochromic lenses are able to change the degree of dimming, or rather, the light transmittance of glasses. After all, the smaller the percentage of visible light that the lens transmits, the darker it is. On the packaging with glasses, this is indicated by the parameter VLT - Visible Light Transmission, or literally "transmittance of visible light". VLT is specified as a percentage: the higher the value, the more transparent the lens. Depending on how much the filter is darkened, it is assigned an index from S0 to S4 corresponding to a certain range of light transmittance:

  • S0 is an almost completely transparent lens that transmits from 80 to 100% of light. They are comfortable to wear indoors, in dim artificial lighting, at night, and in deep twilight.
  • S1 - translucent lenses for cloudy weather, fog, snowfall, and impending twilight.
  • S2 - lenses for variable clouds or the winter sun when it is located low above the horizon.
  • S3 - dark lenses are designed for bright sunlight.
  • S4 is a lens for the highlands with the maximum possible dimming: they transmit only 3-8% of visible light and are designed for climbing in the highlands.

Usually, photochromic filters for sports optics overlap from two to three VLT categories, for example, S2-S3 or S1-S3. S2-S4 lenses are less common.

The principle of operation of all photochromic lenses is the same. A very thin layer of light-sensitive organic matter from the naphthopyrene group is applied to their surface. Its molecules, under the influence of ultraviolet light, slightly change their structure and begin to absorb light, rather than pass it through themselves. This makes the substance layer darker. But as soon as the ultraviolet radiation disappears, the structure of naphthopyrene molecules returns to its original transparent state. As a result of this reversible chemical reaction, the lens becomes darker in the sun and clears up when there is a lack of light.

Torege photochromic lenses

Torege photochromic lenses contain active pigments inside, which can sense the intensity of surrounding ultraviolet rays; always change the color of your lens to match the light conditions. Unlike manual lens replacement, choosing our photochromic lenses can be converted from Category 1 colored lenses to Category 3 colored lenses in less than 15 seconds. Extremely fast color-changing lenses can quickly sense ultraviolet rays at any light intensity. The excellent color-changing and timing characteristics of the lenses are currently the lenses with the fastest color-changing response, providing clear line-of-sight colors that ordinary lenses cannot achieve.

Torege color-changing lenses automatically adjust to changing light, darken while doing outdoors, and restore clarity when indoors.

Currently, we are working on the new photochromic sunglasses, so stay tuned for updates on our website.

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