This filter transmits wavelengths corresponding to the red LED.
When the red 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.
These wavelengths are used by mid- and high-end high-intensity red laser pointers. As this filter has a relative luminous efficiency twice more than the ordinary red laser pointer (650nm), it significantly increases brightness without increasing brightness.