An experimental approach is demonstrated for the mode transformation of cylindrical vector (CV) beams in the far field. This approach is based on the cost-effective fabrication of a thin dielectric film that precisely transforms the single-ring-shaped mode of CV beams into the double-ring-shaped mode with a switchable intensity ratio among the rings. Further, this film also increases the dark core size of the fundamental mode more than two times in a controlled manner, resulting in a dark spot space around the focus in the far field. In contrast to earlier research, our method does not employ tight focusing conditions to generate a dark spot with vector beams, which will be an advantage to the optical trapping of the low-refractive-index particles at more considerable distances from imaging systems.