Contrast transfer function
![Power spectrum (Fourier transform) of a typical electron micrograph. The effect of the contrast transfer function can be seen in the alternating light and dark rings (Thon rings), which show the relation between contrast and spatial frequency.](/Images/godic/202501/06/Contrast_transfer_function5910.jpg")
![TEM Ray Diagram with Phase Contrast Transfer Function](/Images/godic/202501/06/page1-220px-TEM_Ray_Diagram_with_Phase_Contrast_Transfer_Function.pdf5910.jpg")
![CTF Function prepared via web applet created by Jiang and Chiu, available at http://jiang.bio.purdue.edu/software/ctf/ctfapplet.html](/Images/godic/202501/06/page1-220px-Unmodified_CTF.pdf5910.jpg")
The contrast transfer function mathematically describes how aberrations in a transmission electron microscope modify the image of a sample. This contrast transfer function (CTF) sets the resolution of High-Resolution Transmission Electron Microscopy (HRTEM), also known as phase contrast TEM.