contrast-transfer function

optics

Also known as: contrast-transfer curve

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June 24, 2026

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The contrast-transfer function (CTF) in optics is a way to describe how well an optical system can reproduce the contrast of an object at different spatial frequencies. It's essentially the Fourier transform of the system's intensity impulse response.

Conceptually, an object can be broken down into a series of cosine functions. An optical system affects these components by changing their contrast and phase. The CTF quantifies this change for each spatial frequency. By knowing the CTF, one can determine how an optical system will image a given object by analyzing how each frequency component of the object is transformed. Frequencies for which the CTF is zero will be completely lost in the image. This concept is crucial in understanding image formation and is utilized in optical processing and filtering techniques.12

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technology of photography
Resolving power and contrast-transfer function
…image depends also on its contrast. Opticians, therefore, often plot the contrast with which the image is reproduced against the line spacing of that image. The resulting contrast-transfer curve, or function, gives a more reliable indication of the lens performance under practical picture-taking conditions.
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…image depends also on its contrast. Opticians, therefore, often plot the contrast with which the image is reproduced against the line spacing of that image. The resulting contrast-transfer curve, or function, gives a more reliable indication of the lens performance under practical picture-taking conditions.
Read More