What's the difference between ultraviolet and polarization? Under what circumstances do you usually use UV? When to use polarization?

UV mirrors, also known as ultraviolet filters, are usually colorless and transparent, but some will appear purple or purplish red at some angles because of antireflection films. Many people buy UV mirrors to protect the precious lens coating, which is actually only an accessory function. The main function of UV mirror is to absorb ultraviolet rays with wavelength below 400 nm, and it has no filtering effect on other visible/invisible rays. Ultraviolet rays can be filtered because the lens contains lead, so the ultraviolet lens is heavier than other lenses of the same size and thickness. UV mirror is suitable for shooting in seaside, mountains, snowfields and open areas, which can weaken the blue tone caused by ultraviolet light. At the same time, for digital cameras, it can also eliminate the interference of ultraviolet rays on CCD, which is helpful to improve the definition and the effect of color reproduction.

When purchasing a UV mirror, it should be noted that the lens cannot be color cast. After the camera is equipped with this filter, the wide-angle end, especially the telephoto end, can be clearly focused. In addition, if you just want to protect the camera lens from damage, you can also choose a special lens protection mirror instead of UV mirror. Because the lens protection mirror adopts multi-layer coating technology, the transmittance is much better than that of most UV mirrors, so the characteristics of the original lens can be completely preserved.

Polarizers, also known as polarizers, can be divided into circular polarization (cpl) and linear polarization (pl). Polarizer is an accessory of camera. Light itself is an electromagnetic wave. After reflection and diffusion, the vibration in a certain direction will weaken, thus becoming polarized light. Therefore, the reflection of the smooth surface and the diffused light in the sky are polarized light, which will affect the clarity of photographic imaging. The polarizer can choose to let the light that vibrates in a certain direction pass through, so it can weaken the reflection on the surface of the object, highlight the blue sky and white clouds and darken the sky. It is very useful in still life photography and landscape photography.