UV filters are needed to block UV rays. Such filters are used as a device in film cameras, and in sunscreen lotions and creams in the form of special substances. To understand how they work, you first need to understand what ultraviolet light is and why you need to block it.
The spectrum of light visible to the human eye ranges from red to violet. Red light has the longest wavelength, while violet has the shortest. If the wavelength is longer than red, then it is called infrared. If it is shorter than violet, then it is called ultraviolet. The wavelength of light is measured in nanometers.
Light with a wavelength shorter than 400 nanometers is called ultraviolet light. If the wavelength is longer than 700 nanometers, we are talking about infrared light.
UV filters for cameras
Why trap UV light when shooting? The answer lies in understanding how film works in a camera. There are three light sensitive layers. One of them reacts to green light, the other to red and the third to blue. The last layer reacts not only to blue light, but also to ultraviolet light. If there is a lot of ultraviolet light around, then the end result gives more blue in the picture than we would like.
Since the film is not sensitive to infrared light, no filter is required for it. Interestingly, digital sensors are sensitive to infrared radiation, and digital cameras have an appropriate filter.
Ultraviolet radiation is usually low at sea level. There is some amount that causes sunburn, but mostly it dissipates in the atmosphere. If you go higher into the mountains, then the amount of ultraviolet radiation will increase. In this case, the UV filter will be able to prevent the appearance of a blue cast in photographs.
UV filters in sunscreens
Ultraviolet rays can harm human skin. These are burns and long-term skin damage. How strong the radiation will be depends on many factors. This is the proximity to the equator, and the time of day, and the weather, and the season, and the altitude. Being in the shade will be a good protection from ultraviolet radiation, but even this does not always save.
The most dangerous for human health are UVA and UVB rays.
For reliable protection from ultraviolet rays, special creams and lotions containing retention filters are used.
Sunscreens and lotions include two types of active ingredients. Inorganic particles such as titanium dioxide or zinc oxide form a physical barrier, repelling and scattering ultraviolet waves. Organic components, on the other hand, absorb ultraviolet light and convert its energy into heat.
