EOTFs

EOTF stands for Electro-Optical Transfer Function. It describes the relationship between the luminance of a display and the signal voltage it receives. Essentially, it's how a display translates digital video data into visible light. Different display technologies, such as LCD, OLED, and CRT, have their own unique EOTFs. Understanding the EOTF is crucial for accurate color reproduction and ensuring that the image displayed matches the intended creative vision.

The EOTF is the inverse of the OETF (Opto-Electronic Transfer Function), which describes how a camera captures light and converts it into a digital signal. Ideally, a display's EOTF should be the perfect inverse of the camera's OETF to achieve a faithful reproduction of the original scene. However, in practice, display EOTFs are often designed to compensate for the non-linear response of the human eye. Our eyes perceive brightness logarithmically, meaning we are more sensitive to changes in darker areas than in brighter areas.

Gamma correction is a common method used to approximate the EOTF. A gamma value of 2.2 is frequently used as a standard for displays, aiming to provide a perceptually uniform brightness across the entire tonal range. However, modern display standards and workflows, like HDR (High Dynamic Range), utilize more sophisticated EOTFs such as PQ (Perceptual Quantizer) and HLG (Hybrid Log-Gamma). These newer EOTFs are designed to better represent a wider range of luminance levels and improve the viewing experience for high-contrast content. The specific EOTF employed affects how detail is preserved in both shadows and highlights, and influences the overall contrast and perceived sharpness of an image.