The new MC-21 mount adapter allows the use of interchangeable lenses with Sigma SA and Sigma EF mounts on camera bodies with the L-Mount. The MC-21 mount adapter is not compatible with Leica SL, CL, and TL2. When used with Panasonic Lumix S1 and S1R, only the AF-S function operates in autofocus mode. The AF-C function cannot be selected. In the past, there were various methods that enabled lenses from one camera system to be used on bodies of another system. However, today's digital camera systems are much more complex, making it a challenging task to develop a mount adapter that aligns both the mechanical components and the software requirements of lenses and cameras. Even greater difficulties arise when developing an adapter that allows the attachment of lenses designed for DSLR cameras to mirrorless interchangeable lens camera bodies. There is a significant demand in today's photography market for such an adapter that not only adjusts the flange distance but also maintains full functionality.