"If you have a SLR or DSLR camera and other maker/mount lenses, the FotodioX Mount Adapters allow you to use your lenses on the film/digital camera body. Sharing lenses has some distinct advantages. Certain prime lens just can't be replaced and you save the cost of purchase on new lenses. Fotodiox offers a range of adapter from large format to smaller format digital adapters. Adapting larger format lens to smaller format sensors (i.e.: large format to medium format, medium format to 35mm, 35mm to micro 4/3) provides excellent edge-to-edge sharpness. The smaller image field helps minimize the effects of lens distortion and aberration by using the 'sweet spot' or center of the larger lens image circle. This Fotodiox Pro lens mount adapter is made with high standard precision. The all metal design and polished surface is designed to guarantee a smooth mounting and long lasting experience. This adapter allows all M42 Screw Mount Lenses to fit on a Canon EOS camera body. The enlarged lip of the adapter is designed to depress the aperture pin of the lens to allow full aperture control on M42 lenses. Although the lens will fit physically, automatic diaphragm, auto-focusing or any other functions will not operate correctly while using this adapter. In this case ""stop-down mode"" will need to be used when metering since the lens does not have the ability to have its aperture controlled by the camera body. You can shoot with manual mode or aperture priority mode. Infinity"