> On Feb 22, 2017, at 12:36 PM, Mark Roberts <postmas...@robertstech.com> wrote: > > John wrote: > >> Or else Google translate just has a dirty mind. >> >> What I need explained is why new lenses are so much longer than the old >> ones of the same focal length? > > Every lens design is the result of many compromises: Small vs. large, > expensive vs. cheap, tack-sharp vs. just-sharp-enough. As sensor > resolution (and pixel peeping) increase it pushes lens designers > towards ever more demanding optical requirements and something has to > give in this case it's size/weight. So we gain optical resolution > and lose light weight and compactness. Reducing light falloff in the > corners generally requires larger diameter lenses and in the age of > pixel-peeping people are more critical of that than ever (which is odd > because it's easier than ever to correct in post). > > -- > Mark Roberts - Photography & Multimedia > www.robertstech.com >
I wonder about one other factor - with internal focus the external lens will be longer to accommodate the (internal) movement of the focusing elements. Yes? stan -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.