This filter transmits wavelengths corresponding to the orange LED.
When the orange LED light source is used to illuminate the subject, this filter can be used to cut off all wavelengths except the light source, thereby improving the contrast.
The orange color resembles the color emitted by sodium lamps in tunnels and the wavelengths are also called D-lines. The long wavelengths ensure high transmittance in environments where thick fog or dense dust is present.
The absence of UV wavelengths prevents the lamps from attracting insects such as moths.
