Tokina Kenko intermediate ring set DG Sony

Extension tubes are designed to enable a lens to focus closer than its normal minimum focusing distance. Getting closer magnifies your subject, making it appear larger in the viewfinder and in your pictures. They are exceptionally useful for macro photography, allowing 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. They are mounted between the camera body and lens to create more distance between the lens and film plane. By moving the lens farther away from the film or CCD sensor in the camera, the lens is forced to focus much closer than normal. The greater the length of the extension tube, the closer the lens can focus.