What are the most commonly used filters for SLR cameras?

Commonly used filters are uv mirror, nd mirror, gradient mirror and cpl.

Uv filter, also called ultraviolet filter, can weaken the blue tone caused by ultraviolet rays, prevent UVa and UVb from entering the lens and affecting the imaging, help improve the image clarity and color effect, and protect the lens surface from damage.

CPL filter, also called circular polarization, mainly filters polarized light reflected from nonmetallic surfaces. When the CPL mirror rotates, it can make the sky bluer and increase the color saturation. It can also reduce the soft focus caused by large fog in landscape photos, but it does not change the tone balance of the whole picture.

Gradient filters generally have three colors: gradient grey mirror (GC-GRAY), gradient blue mirror (GC-BLUE) and gradient orange mirror (GC-ORANGE). The function of the gradient mirror is only on one side, and it has no effect on the photo on the other.

Neutral density filter is also called medium gray density mirror. The main purpose of using neodymium mirror is to prevent overexposure. If the light is too bright, it is difficult to choose a slower shutter speed.