Paul McCartney has been having exhibits recently of photos he took himself on early Beatle tours with his Pentax SLR. I think these have been published in a book too. One can find interviews of him about this on Youtube. Recommended for Beatles fans (I am/was one!)
Pentax was a very popular brand in England at the time. John Hedgecoe well know photographer, did a portrait of
Queen Elizabeth II, among others. Can't get any better than that. In his books Hedgecoe always used Pentax equipment. He shot the Beatles. This may had something to do with their selection.