What are two main reasons that humans have a high frequency contrast cutoff?

Humans have a high frequency contrast cutoff primarily due to optical limitations and the density of photoreceptors. The optical limitations stem from the eye's inability to refract high-frequency visual information accurately, which can result in the blurring of fine details. The components of the eye, such as the lens and cornea, can introduce aberrations that limit the highest frequencies that can be perceived.

In addition, the density of photoreceptors, particularly cone cells responsible for color vision and high acuity, plays a crucial role. A higher density of photoreceptors means that the visual system can detect finer details in the visual scene. However, there is a limit to how finely these details can be resolved, and that cutoff occurs at certain spatial frequencies.

This combination of optical limitations and the characteristics of photoreceptor density dictates that there is a particular threshold beyond which the human visual system is less effective in detecting contrast, leading to the high frequency contrast cutoff.