The modulation transfer function( MTF), also known as the contrast transfer function, is a characteristic value of camera lenses. The aim is to represent the finest object structures as realistically as possible.
For this purpose, the lenses record line pairs of black and white lines whose distance varies. It varies from a larger distance of one line pair per millimeter to ten adjacent line pairs per millimeter. The MTF function is used to determine whether the lines are still individually recognizable or appear washed out. For this purpose, an MTF value is determined from the quotient of the image contrast to the object contrast and plotted as a function in a Cartesian coordinate system. The Y-axis is the contrast, given as a percentage, the X-axis is the line pairs per millimeter.