I am looking for a more affordable (than a Metaabones) speed booster for my nice collection of Nikon lenses that I have. What brands are recommended? I know Metabones makes an active mount (autofocus/stabilization) but not one for the Nikon. Is there an active mount available for the Nikon F mount? I only have cheaper, kit lenses for Canon and it would not be worth purchasing a speed booster for them.