MTF (Modulation Transfer Function)

MTF is a function describing how well an optical system transfers image contrast depending on the spatial frequency of the details — the higher the MTF value at a given frequency, the more clearly fine details are reproduced.

How is MTF interpreted?

An MTF plot shows contrast (on a 0–1 scale) as a function of spatial frequency (line pairs per millimeter). An ideal optical system would have an MTF of 1 for all frequencies — in practice MTF decreases as frequency increases, until it reaches zero at the system's cutoff resolution, limited by diffraction and aberrations.

Applications

MTF is the standard criterion for assessing the quality of photographic lenses, microscope systems, and satellite imaging systems, allowing an objective comparison of different optical designs in terms of real image sharpness.

Related terms

Spherical aberration

Sequential ray tracing

Numerical aperture