> For a long time a f2.8 lens stopped down to f8 was likely to produce a better image than a f4 lens stopped down to f8--simply because the f2.8 was built bette

> For a long time a f2.8 lens stopped down to f8 was likely to produce a better image than a f4 lens stopped down to f8--simply because the f2.8 was built better. And at the same time it was just as likely to result in poorer pictures because of focus shift when stopped down.