What is the maximum number of gray levels that the human eye can distinguish?

The human eye is capable of distinguishing approximately 100 different shades of gray. This ability is influenced by various factors, including the conditions under which light is perceived and the environment. In optimal lighting conditions, the eye can differentiate details and subtle changes in contrast and texture among these shades.

Understanding this limit is particularly important in fields where precise image interpretation is critical, such as medical imaging and dosimetry. Various imaging techniques often utilize contrast and shading to represent different levels of tissue density or radiation dose, thereby affecting how images are interpreted by professionals. Recognizing that the eye's resolution for gray levels is near this benchmark aids in the development of effective visual displays and informs standards for image quality in medical contexts.