Neutral density filters (absorption type) absorb light that is not transmitted, thereby uniformly reducing the transmittance of a certain part of the spectrum. They can be used to avoid damage to camera sensors or other optical components caused by strong light, and are usually used for imaging or laser applications. Neutral density filters (absorption type) generally refers to a material itself or doped with certain elements, which absorbs light of specific wavelengths and has little or no effect on light of other wavelengths. The damage threshold of the neutral density filters(absorption type) is usually lower, and after long-term use, there may be heating phenomenon. Attention should be paid when using them.