Orthochromasia

[2]: 20  Vogel experimented with adding small amounts of certain aniline-based dyes to photographic emulsions to extend their sensitivity beyond blue light.

This breakthrough allowed for the production of emulsions that could capture a broader spectrum of colors and tones including Josef Maria Eder, who introduced the use of the red dye erythrosine in 1884.

[3] In addition to their use in still photography, orthochromatic films also played a significant role in the early days of motion pictures.

The improved tonal range provided by orthochromatic emulsions allowed filmmakers to create more visually compelling and realistic moving images.

A cyan photographic filter, which blocks red light but allows blue and green to pass, can be used with standard panchromatic film to produce a similar effect.