Sensitivity in photography refers to the degree to which a photographic emulsion responds to light exposure. Higher sensitivity materials require less light to produce an image, while lower sensitivity materials need more light but can deliver finer detail and smoother tonal gradation.
Photographers choose the sensitivity of film or digital sensors based on shooting conditions, desired depth of field, and image quality. Understanding sensitivity is key to controlling exposure, achieving correct lighting, and capturing images with the intended sharpness, contrast, and detail.