365nm CWL,OD4,FWHM 8nm, Narrowband Filter

CWL simply signifies the wavelength at the center of the filter's passband.

FWHM stands for Full Width at Half Maximum. It describes the bandwidth of the filter, representing the range of wavelengths over which the filter transmits light at least half of its peak intensity. Think of it as the width of the "window" that the filter opens for specific wavelengths.

Peak Transmission (Tpk) refers to the maximum percentage of light transmitted through the filter at its center wavelength (CWL). It essentially tells you how much light, at the most favorable wavelength, can pass through the filter compared to the original light source.

Optical density (OD) describes the filter's ability to attenuate light, specifically within the wavelengths it blocks (known as the stopband). It essentially tells you how much light is blocked by the filter at those wavelengths.