The Kenko Auto Extension Tube Set DG consists of a 10mm and 16mm extension tubes that can be used individually or together. The Kenko extension tubes have all the contacts and circuitry to maintain communication between the camera body and the lens. AF (within the limited macro range) and auto exposure are maintained with these extension tubes. Extension tubes are designed to enable a lens to focus closer than its normal set minimum focusing distance. Getting closer has the effect of magnifying your subject (making it appear larger in the viewfinder and in your pictures). They are exceptionally useful for macro photography, enabling you to convert almost any lens into a macro lens at a fraction of the cost while maintaining its original optical quality. The DG extension tubes have no optics.