The lens used is a Russian copy of a Zeiss Biotar, which were much cheaper than $50 in the not so distant past, but most any inexpensive normal lens off of ebay should work fine, including (TTL) AF, even with a common DSLR kit lens. Old prime SLR lenses of obsolete mounts, or ones not commonly used with adapters can still be had for a few bucks and up, and are a decent option for those on a budget.