Typically this would be glass but metal, plastics, and other materials are also often used. Bandpass filter Transmits light in usually small band of wavelengths and rejected light above and below the selected band. The passband is usually referred to as the area of transmission and the areas above and below are known as rejection bands. A notch filter is the opposite of a bandpass filter. A magenta filter that transmits red and blue will have the green color bands notched out.
Contamination Is a small amount of light spuriously transmitted from within a rejection band.
This leak may or may not affect the perceived color of the filter. Adhesion Refers to the measure of force necessary to detach an area of film from the substrate or from a neighboring film in a multilayer coating. A piece of tape is stuck to the film and peeled off. The film fails if a significant portion of the coating comes away when the tape is peeled off. The measure of how the length and volume of a type of glass changes in response to an increase or decrease in temperature.