over look developed when the filmmakers  realized the extreme difference in height between  Christopher Lloyd (I) (qv) and Michael J. Fox (I) (qv); Fox is  54 1/2" while Lloyd is 61". To compensate for the height  difference, director Robert Zemekis (qv) used specific blocking  where the two often stood far apart at different camera depths. For  close ups, Lloyd would have to hunch over to appear in frame with  Fox. The same approach was used in the two subsequent sequels.