- Shielding sensitive scientific and medical devices from the magnetic field environment is one of the promising applications of superconductors. Magnetic field concentration by superconducting magnetic lenses is the opposite phenomenon based, however, on the same properties of superconductors: their ideal conductivity and ability to expel the magnetic field. Full-dimensional numerical simulations are necessary for designing magnetic lenses and for estimating the quality of magnetic shielding under arbitrary varying external fields. Using the recently proposed Fast Fourier Transform based three-dimensional numerical method [Prigozhin and Sokolovsky, Supercond. Sci. Technol. 31, 055018 (2018)], we model performance of two such devices made of a bulk type-II superconductor: a magnetic shield and a magnetic lens. The method is efficient and can be easier to implement than the alternative approaches based on the finite element methods.