The Lensbaby Sweet 50 Optic is made for use with the Composer Pro, which can be bought separately, or used interchangeably with the Sweet 50 if you own it already with a different optic. It is a selective focus lens that uses a curved field of focus optic to create a blurred effect around the focus spot. The 50mm focal length lens has two multi-coated glass elements in one group, and an aperture range of f/2.5 to f/22. The 12-blade internal aperture is easily controlled via a ring on the front of the optic. The sharp sweet spot of focus can be moved within the frame by tilting the Composer Pro's ball-and-socket joint. The size of the sweet spot is also controlled by changing the aperture.