Publisher Summary This chapter discusses two methods for the determination of the imaging properties of electron-optical systems with a photocathode. The determination of the imaging properties of electron-optical systems for transferring the electron image from the photocathode to the target of a TV camera tube or to the luminescent screen of an image intensifier is a rather complicated problem. This chapter briefly describes two methods for determining the imaging properties of the electron-optical system of an X-ray image intensifier with variable magnification. These are the experimental method, based on the use of a demountable model of the tube to be investigated, and the computational method, utilizing programs prepared in advance for the determination of imaging properties of the given electron-optical system with the aid of a National-Elliott 503 computer. The chapter elaborates a diagrammatic cross-section of the demountable model of the X-ray image intensifier with variable magnification. The computational method is also discussed, in which, to determine the imaging properties of the electron-optical systems by means of a computer, a program was prepared for the solution of the problem of both the distribution of the electrostatic field and the form of the electron trajectories in a rotationally symmetrical electrostatic field.