Varifocal lenses provide a flexible solution to applications that previously would have required multiple fixed focal length lenses. Simply adjust through the indicated focal length range for the desired field of view, within the specified working distance range, and then set focus for best image. Due to the variable focal length range, varifocal lenses are also known as vari-focal, variable-focus, or multi-focal lenses. Varifocal lenses can select the focal length within the specified range like zoom lenses, but unlike a zoom lens focus adjustment is needed after setting of the focal length. They have a different, simplified optical and mechanical design that is more cost-efficient to produce than zoom lenses. The focal length adjustment is typically a middle or rear assembly of elements that slides back and forth, whereas the separate focus adjustment is typically a front cell movement.
#57-680 is a high resolution, low distortion lens for MegaPixel cameras.
Note: CS-mount lenses are not compatible with C-mount cameras.