I am reading a book "A Light Affliction: a History of Film Preservation and Restoration" which says: During preparation for the Blu-ray release of The Wizard of Oz, technicians at Warners became aware that wire-work used for the Cowardly Lions tail and the winged monkeys would be clearly visible on the discs. The restorers sought the advice of Robert A. Harris who responded, "If 1939 audiences didnt see that wires when they saw the film in theatres, then present day audience shouldnt see them on Blu-ray".
My question is: how is it possible that you can you see some details on HD which you cant see on the original film? This doesnt make sense to me. 35mm film has much higher resolution than HD, right?