The role of the filter

A filter is an optical device used to select a desired band of radiation. One of the commonalities of the filters is that no filter can make the imaging of the celestial body brighter, because all filters will absorb certain wavelengths, thus making the object darker.

color filter
This is a flat glass or bright film of various colors with a transmission bandwidth of hundreds of angstroms, mostly used in broadband photometry or installed in stellar spectrometers to isolate overlapping spectral levels. Its main feature is that the size can be made quite large.

thin film filter
Generally, the wavelength is longer and is mostly used as an infrared filter. The latter is on a certain film base.

The role of the filter is great. It is widely used in photography. Why is the main scene always so prominent in the landscape paintings taken by some photographers? How do they do it? This uses filters. For example, if you want to use your camera to start shooting a yellow flower with blue sky and green leaves in the background, you cannot highlight the theme of "yellow flower" because the image of yellow flower is not prominent enough. However, if a yellow filter is placed in front of the lens to block the green light emitted by a part of the green leaves and the blue light emitted by the blue sky, while allowing the yellow light emitted by the yellow flowers to pass through in large quantities, the yellow flowers will appear very obvious and highlight the theme of "yellow flowers.