Salt Lake Tribune | 1918-01-06 | Page 33 | Auto Movie Picture Puzzle is Explained

AUTO II PICTURE PUZZLEjSEXPLAlniED Seeming Anomaly of Backward Back-ward Rotating Wheels Is Made Clear. "Why do automobile and wagon wheels in motion pictures seem to turn backward?'' This question has been akc l many times and s. en s to be one thut has pu.zleil most persons for :-:omo time. Thousands h.;ve been mytii'ied hy tins seeming anomaly, y?r. th? reason is vry simpl'-. m Th camera with which the. pictures arc taken has a black dis.- wirh circular circu-lar holes around its circumference. This turns rapidly !:ehiml thu lens, each hole rcstifg for a fraction ot a ;--eco!:d, in which time a picture is iaketi on the f i 'in. Thus a series of pict urcs is taken, which, when pased rapidly in front of a liht, produces the effect of a moving picture, though this, is really not hing but a scries of instantanc- ous snapshots showing successive positions posi-tions assumed by the moving object. But the successive positions may easily produce an entirely false effect. When the film is run off and thrown " on the screen the spoke will seem to run (backward. No matter how many spokes I there are on Ihe wheel, it is evident j that the effect on each one will be the same, ami the entire wheel will ap-par ap-par to turn backward ut the same speed as t hat of each spoke. The so-called mystery is nothing more than an optical illusion.