JJC Auto Focus (AF) Extension Tube with TTL Exposure for Close-up Image Photography for Nikon F Mount DSLR & SLR Cameras (12mm/20mm/36mm Set)\nDescription\nThe Auto Focus Extension Tube Set (or the Tube being used standalone) allows your lens to focus closer than its normal minimum focus distance. By placing distance between your camera body and lens, focusing distance is shortened and the effect of magnifying your subject is created. Extension tubes enable macro performance for lenses not otherwise able to focus that close, and are also suited for close-up portraiture.The Auto Focus Extension Tube Set for Nikon F Mount contains three extension tubes of 12mm, 20mm and 36mm lengths. They can be used individually or together to create the desired magnification effect.For closer focusing use the larger extension tube or stack the tubes together. It is even possible to stack these tubes with others from another set. Extension tubes have no optical elements so they do not degrade the m