Which type of filter transmits only long wavelengths leading to altered color perception?

A long-pass filter is designed to transmit light that is above a certain wavelength threshold, effectively allowing only the longer wavelengths to pass through while blocking shorter wavelengths. This selective transmission results in altered color perception because the shorter wavelengths, which are responsible for colors such as blue and green, are significantly attenuated or eliminated. Consequently, when a long-pass filter is used, the observer experiences a distortion in color perception, predominantly viewing warmer colors, such as reds and yellows, while the cooler colors are diminished.

In contrast, narrow band filters typically transmit light within a tight range of wavelengths, often for the purpose of isolating specific colors, rather than exclusively allowing all long wavelengths. Interference filters work based on the principle of optical interference and are used to transmit a specific wavelength or range of wavelengths with very precise control, not merely to filter for longer wavelengths. Broad band filters allow a wide range of wavelengths to pass without significant attenuation, affecting color perception less dramatically.

Understanding the characteristics of these different types of filters highlights why the long-pass filter is particularly impactful on color perception by emphasizing only longer wavelengths.