The Sons of Great Bear
It was inevitable that the characters from May’s Western adventures would eventually make their way to the big screen, and, in 1962, West Germany’s Rialto Film Preben-Philipsen made it so, initiating a series of films that were to become wildly popular throughout Europe. The majority of these starred French actor Pierre Brice in the role of Winnetou and American actor—and former Tarzan—Lex Barker as Old Shatterhand, and used locations in Yugoslavia to sub for the American West. Eventually coming to comprise eleven entries in all, they came to be known as the Winnetou films, and are generally considered to be the seed from which the Italian Spaghetti Western sprang, a connection driven home by the presence within them of such genre stalwarts as Klaus Kinski and Terence Hill.
Needless to say, the Winnetou films used non-Indians to play Indians--a great example of "redface." I haven't seen any of them yet, but foreign films based on foreign books about what Indians were like can't be too good.
For more on the subject of Karl May and Germans, see:
Germans think they own Indian culture
Surveyors = evildoers
Karl May's "wild" West
Why Germans love Indians
New Karl May exhibit
For more on the subject in general, see The Best Indian Movies.