A device with characteristics of selective transmittance, capable of passing a certain part of the electromagnetic spectrum while being opaque to the other portions. Means of producing filters varies considerably. Color filters (for the visual) usually consist of glass, gelatin or plastic containing dyes or pigments. Band pass filters are found in signal processing and are commonly fabricated via electronics and complex circuitry and are designed to pass and reject parts of the spectrum based on the value of its frequency in comparison to the cutoff frequency. For a high pass optical filter, high-frequency signals are transmitted while frequencies lower than the cutoff frequency are rejected, and low pass filters are the opposite.