CH. XI] PRECAUTIONS FOR MOVING PICTURES 427 



592b. Table showing Speed at which flicker just disappears. 

 FROM T. C. PORTER 



Flashes per second 



Illumination Logarithm of at which flicker 



meter candles illumination just disappears 



.0625 8.796-10 17.75 



.in 9.046-10 18.08 



.25 9.398-10 18.50 



i.oo o.ooo 25.08 



4.00 0.602 33.50 



1.56 0.193 28.00 



2.70 0.431 32.00 



6.30 0.799 35-50 



25.00 1-398 42.66 



IOO.OO 2.OOO 5O.I6 



IOO.OO 2.OOO 5O.83 



178.00 2.250 55.08 



400.00 2.602 56.42 



1600.00 3.204 65.00 



6400.00 3.806 71.00 



RESULTS FOUND BY THE AUTHORS WITH A MOVING" PICTURE OUTFIT 

 32.00 1.500 36 



IOO.OO 2.OOO 41 



1000.00 3.000 50 



3200.00 3.500 54 



The curves (fig. 234) are drawn to show the speed at which 

 flicker disappears for equal light and dark flashes. There is not a 

 great advantage as far as the speed at which flicker disappears in 

 having the duration of the dark flash very short. The actual 

 appearance of flicker is much less violent, however, when the dark 

 section is narrow. 



GENERAL PRECAUTIONS 



593. Inspection of films. Before attempting to show films 

 to an audience, it is well to inspect them carefully to see that they 

 are in good condition and wound on the reel correctly. 



Use the rewinder to roll the film from the new reel upon an empty 

 reel. Turn the handle slowly with one hand while holding the 

 edge of the film between the fingers of the other hand; do not touch 

 the face of the film. When a patch is met in the film inspect it 

 carefully to see that: (i) The same side of the film is on top. (2) 

 The patch is made at the right place so there will not be a misframe, 



