The modulation transfer function (MTF) is a measure used to evaluate lens performance by comparing the contrast of a test chart with the contrast of its reproduced image. It provides a quantitative assessment of how well a lens can render fine details and distinguish between subtle variations in tone and sharpness.
MTF is commonly used in the design and manufacturing of photographic lenses, helping engineers and photographers understand a lenss resolving power and optical quality. High MTF values indicate superior performance, with crisp, detailed images, while lower values suggest a loss of contrast and detail, especially in the finer areas of the image.