Which statement best defines MTF?

• A. MTF measures the average brightness of an image
• B. MTF measures image sharpness at a single frequency
• C. Higher MTF values indicate greater fidelity across frequencies
• D. MTF is unrelated to image quality

Answer: (C)

MTF, or Modulation Transfer Function, describes how well an imaging system preserves contrast as details get finer. Spatial frequency is the level of detail in the image—the more cycles per unit of image width, the finer the detail. The MTF is a curve that shows how much contrast is transmitted at each frequency. When MTF values are higher across frequencies, the system retains more of the original contrast for both coarse and fine details, leading to a sharper and more faithful image. That’s why this statement is the best definition: higher MTF values indicate greater fidelity across frequencies. In contrast, average brightness is about luminance, not how well contrast (modulation) is transmitted; MTF is defined over a range of frequencies, not just one; and it is directly related to image quality.