What is a shortpass filter?


A short-pass filter is an optical filter that only allows incident light below a certain wavelength to pass through – the so-called cut-off wavelength. It blocks light above this wavelength. In addition to the cut-off wavelength, important for the shortpass filter are the transmission band and the actual blocking band in which the short-pass filter is still permeable to a small part of light.

Short-pass filters are available both as interference filters and as coloured glass filters; the quality of blocking is usually specified in the unit of optical density (OD). One area of application for short-pass filters is, for example, to block IR radiation on camera sensors. In this case the filters are also referred to as IR cut-off filters.

How does a shortpass filter work?

A short-pass filter blocks light that is above a certain wavelength and is only permeable to light below this cut-off wavelength.

What are shortpass filters used for?

Short-pass filters are used, for example, in camera technology to block IR radiation.

How are shortpass filters specified?

Of importance for a short-pass filter are the cut-off wavelength (i.e. the wavelength above which the filter is no longer permeable to light), the actual blocking band, the transmission band, and optical density.