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The modulation transfer function or MTF is a measure of the spatial resolution of an imaging component. The latter can be an image sensor, a lens, a mirror or the complete camera. In technical terms, the MTF is the magnitude of the optical transfer function, being the Fourier transform of the response to a point illumination.
The MTF is not really the most easiest measurement that can be done on an imaging system. Various methods can be used to characterize the MTF, such as the “slit image”, the “knife edge”, the “laser-speckle technique” and “imaging of sine-wave patterns”. It should be noted that all method listed, except the “laser-speckle technique, measure the MTF of the complete imaging system : all parts of the imaging system are included, such as lens, filters (if any present), cover glass and image sensor. Even the effect of the processing of the sensor’s signal can have an influence on the MTF, and will be include in the measurement.