Perhaps the OP has made an error, (oops!, non of us do that, ever, do we?). I only know of the Zuiko 50mm. f3.5 Auto-macro amongst the older series of lenses. This lens is optimized for reproduction at 1:10 but I would find it difficult to detect much difference between it and the Zuiko 50mm. f1.8, other than the aperture size and close focussing caperbility. It has become my 'standard' lens.