In order to maintain focus to infinity the adaptor has a high quality internal lens element. This has the effect of increasing the focal length of the base lens by about 20%. Used with 35mm or full frame digital cameras, lens use is restricted to between focal lengths of about 50-300mm due to coverage problems. When used with digital SLR's having a sub 35mm sensor, the inherent magnification factor on focal length together with the magnification due to the element gives an overall factor of approx 2x.
The adaptor allows manual and aperture priority exposure modes, but with stop down metering and manual diaphragm. The viewfinder image darkens as the aperture reduces.
As far as we are aware, this adaptor is no longer in production - so stocks are limited.
