SUNLENSIS - LE CATEGORIE

Centro Style sun filters meet the essential safety requirements established by Regulation (EU) 2016/425 and the requirements defined by the harmonized standard EN ISO 12312-1:2013/A1:2015 that classifies solar filters into five categories (FC) in relation to the amount of light that passes through the filter, called transmittance. In optics, The transmittance (generally indicated with T or Tv), identifies the capacity of a material to let a part of the incident light pass through it. On the contrary, absorbance (or optical density) is the amount of light that is absorbed by a lens or solar filter. Depending on the use, it is advisable to choose the most appropriate category, as shown in the diagram below:

All people are exposed to a certain amount of ultraviolet (UV) radiation every day, mostly from the sun. UV radiation covers that portion of the electromagnetic spectrum with a wavelength between 100 and 380 nanometers. Light is divided into visible rays, infrared rays and ultraviolet rays. Ultraviolet (invisible) rays are classified into: UV - A (315-380 nm) tanning properties UV - B (280 -315 nm) therapeutic properties UV - C (100 - 280 nm) germicidal properties In general, the penetration capacity and therefore the danger to humans of UV rays, increases as the wavelength decreases and consequently, as the frequency increases. Most of the UV rays that reach the Earth's surface are UVA and a small part UVB, while UVC is totally absorbed by the Earth’s atmosphere. The UV levels are also higher as the altitude increases (every 1000m of height the UV levels increase by 10/12%). Other environmental factors that influence UV values are the ozone layer and the reflective capacity of the Earth's surface (e.g., snow reflects about 80% of UV radiation, dry beach sand about 15%)