K&F SK43 100x100mm Natural Night Square Filter is designed to block the wavelengths of light created by mercury vapor, sodium and other Low CRI lights that are often used as streetlights.
These lights are usually yellow/orange and are the primary cause of light pollution around cities. This makes capturing beautiful nightscapes near cities very difficult.
If you are an ight photographer then you almost certainly have run into the horrible yellow glow of light pollution or the ugly yellow cast that street lights spread over urban nightscapes.
This light pollution and yellow cast can hide stars and mess with the white balance of your scene. KF01.1144