Measurements of tritium concentration on the surface and in depth of various samples of constructional materials employed in nuclear power engineering have been made by making use of a magnetic microscope and a magnetic imager. -radiation images of large (up to 0.5 m) radioactive contaminated surfaces in a nonuniform magnetic field were obtained. The magnetic field uniformly increasing in the direction from the observable surface to the recording screen was used. The principal conditions of identical transfer of the image and its reduction coefficient were determined depending on the ratio of the magnetic fields on the sample surface and the screen. The experiments were carried out in vacuum conditions. The magnetic field was produced with a cylindrical rod of a magnetic material and in the screen area it was 0.5 T. Formation, transport and detection of images were fulfilled in a wide range of their reduction ratio (1-1/40).