The samyang 35mm t15 as umc ii is a fast manual focus video lens for sonys full frame e mount compact system cameras such as the a7 models the lens has been developed primarily for professional video making purposes and features follow focus gearing and a de clicked aperture ring to allow smooth precise control over the focus and aperture whilst filming the t number of 15 refers to the actual light transmission which is more accurate and is particularly important in the film industry w