Sam Haskins was long considered a reknown photographer using Pentax
but I'm not sure I would call him a famous photographer. In my book
he's a "pop" photographer.
Don't forget, back in the 60's, Spotmatics outsold all other brands of
35mm SLR - combined! Hard to believe, but true. There were lots of
'em out there.
frank
And Pentax system ruled in the years just before the Nikon F
appeared. Even after, some nikoneers F-mounted some Takumar fast
lenses (notably the 200/3.5 & 500/4.5 lenses) - at least some working
at National Geographic.
Andre