can anyone supply me with the definition/meaning of the expression "press focus? " i've seen this used to describe lenses listed for sale in Shutterbug, only as a descriptor it is waisted on me - as i don't know what it means. also, some whe re i read where someone said that one shouldn't use a tessar lens below f 11, wh y not? does a tessar design become soft focus at aperatures: 8, 5.6, ...? are "p ress lenses" designed to be sharpest when stopped down to f 8? thanks.