A camera, including: an imaging unit including: an image sensor configured to generate image data; and a phase mask configured to apply a multi-order-helix rotating point spread function, RPSF, on light incident on the image sensor, the light originating from point objects in a scene, wherein the RPSF has peaks which rotate with respect to a reference axis as a function of defocus of the point objects, such that the image sensor generates image data representing a blurred image of the scene in which the point objects are represented blurred in accordance with the RPSF.