Leica camera owners with L-Mount systems rejoice! The Mount Converter MC-21 allows you to use your Sigma SA-mount interchangeable lenses with the Leica L-mount camera body. The gadget incorporates the digital data necessary to provide fast and smooth AF for compatible lenses as well as OS features and functions of the camera that help control peripheral brightness, correct transverse chromatic aberration and distortion.Instead of buying a new Leica compatible lens, buying the Sigma MC-21 Lens Mount Converter (Sigma SA to Leica L-Mount) maximizes the effectiveness of the valuable SA lens you have already invested in. It gives you more freedom by extending the use of L-mount cameras not just from Leica Camera, but also Sigma and Panasonic cameras with L-mounts.Mount Converter MC-21 is ideal for professional photographers who use different camera systems depending on the subject, as well as amateur photographers who enjoy using a variety of camera systems. Increasing the compatibility of lenses with different camera systems makes these assets more valuable than ever.29 Lenses CompatibleThe Sigma MC-21 increases the number of Sigma lenses available for Leica system camera bodies. It makes 29 interchangeable lenses usable with L-mount cameras.It is compatible with autocrop functionality. You can mount an APS-C size image circle DC lens to a 35mm full frame sensor camera and still have immediate use for shooting.Excellent Autofocus PerformanceAF-S mode enables extremely fast, accurate and smooth autofocus performance. The MC-21 Mount Converter is not compatible with AF-C mode.Includes Necessary DataMount Converter MC-21 incorporates the data necessary for each compatible lens and uses a dedicated control program to optimize AF drive, aperture control, and other functions. It is compatible with functions of the camera that maintain peripheral brightness and correct transverse chromatic aberration, distortion, and more. Future lenses will also come pre-loaded with data for operating them with the MC-21, meaning no firmware updates will be needed on the MC-21.Easy-to-Use InterfaceThe LED display on the Mount Converter MC-21 makes it easy to know whether an attached lens is compatible or not. It will light when compatible. The LED also lets you know when a firmware update is available for your lens.Exif Data CompatibilityLens type, focal length, F number and other tags are embedded as Exif data in the image file.Eliminates Internal ReflectionsThe barrel's inside surface is covered with flocking. This guards against reduced lens performance from internal reflections.Includes Tripod SocketThe Sigma MC-21 adapter allows you to attach a tripod. This is useful when using lenses that aren't built with a tripod socket. You can mount the tripod to the MC-21's tripod socket, making your lens tripod mountable.