The Tamron C-Mount 4 to 12mm Varifocal Manual Iris Lens is a varifocal lens which features a 4 to 12mm adjustable focal length. Compatible with cameras using a 1/2" imager size and C-mount, the lens is designed to deliver high-quality imagery. With an aperture range of f/1.4 to close, the lens allows for clear images even in low light conditions. The lens surface is multi-coated for lessening ghosting and flare in backlit conditions and eliminates constructional problems such as lopsided blur and focal point image degradation. The integrated slip-mount mechanism allows you to fine-tune the position after mounting the camera to set the auto-iris meter to a proper position around the lens. With the lock for each control ring (zoom and focus), you can avoid setting displacement after installation.