The lensbaby spark nikon fit is a lightweight all plastic bodied 50mm selective focus lens with a f56 fixed aperture and is designed to be a fun way to capture selective focus images with a digital slr the lensbaby spark features a unique selective focus optic and a tilting lens body allowing the aspiring enthusiast photographer to capture creative images in camera that have a sweet spot of focus surrounded by blur the lensbaby spark is compatible with the rest of the optics in the optic