PHOTOGRAPHIC MATERIALS 



137 



print. Most 16-mm. films are put through a reversal process to obtain a positive 

 image on the same film that was exposed in the camera. However, there are films 

 available for the regular negative-positive processing. Emulsions of various speeds 

 and with both orthochromatic and panchromatic sensitizings are available, as well as 

 several direct-color films. 



For sound recording on 16-mm. film, the perforations are omitted from one side, 

 making this space available for the sound track without encroaching on the picture 

 area. Thus the regular silent film can be run in sound projectors without any change 

 in size or position of the projection aperture. Sound film cannot be used in silent 

 projectors unless they are fitted with special sprockets and pulldown claws operating 

 on only one side of the film. 



STANDARD 3S-MM. FttM 



CtTTTlNO AND PERPORATinO DIUBNSIONS 

 or BZCATIVS ADD POSITIVE KAW STOCK 



These dimensions and tolerances apply to the material im- 

 mediately after cutting and perforating. 



Inches 



1.378 + 0.000 



-0.002 



1.109 * 0.002 



0.134 * 0.002 



0.187 * 0.0005 



0.110 * 0.0003 



0.078 * 0.0003 



Not > 0.001 



0.020 approx. 



18 70 =<■ 0.015 



Millimeters 



35.00 + 0.00 



-0 05 



28.17 * 0.05 



3.40 « OS 



4.75 * 0.013 



2.79 * 008 



1.98 ■• 0.003 



Not >0 025 



0.51 approx. 



475.0 * 0.381 



* L « the lengtb of any 100 consecutive perforation intervals. 



STANDARD 16-MM. FILM 



CDTTIHO AHD PERFORATIHO DIHEHSIOKS 

 OF HEGATIVB AND POSITIVE RAW STOCK 



These dimensions and tolerances apply to the materia] im- 

 mediately after cutting and perforating. 



Inches 



0.630 + 0.000 

 -0.002 

 0.485 * 0.001 

 0.072 * 002 

 300 ± 0.0005 

 0.072 * 0.0002 

 0.050 * 0002 

 Not > 0005 

 0.010 approx. 

 30.0 * 0.03 



MiUimeters 



16.00 + 0.00 

 -0.05 



12.32 * 0.025 

 1.83 * 0.05 

 7.62 * 0.013 

 1.83 * 0.005 

 1.27 * 0.005 

 Not > 0.013 

 0.26 approx. 



762.0 •^ 0.76 



* L M the length of. any 100 consecutive perforation intervals. 



Fig. 10. — Dimensional standards for 35-mm. and 16-mm. film as standardized in the United 



States of America. 



The 8-mm. film was derived from the 16-mm. size in an attempt to lower the film 

 cost to amateurs. Since the picture area is only one-fourth that of the 16-mm. film, 

 graininess and resolving power are very important, and it is necessary to use specially 

 prepared and very thinly coated emulsions. There are two 8-mm. systems in use. In 

 one case, the film is originally 16-mm. wide, and it is run twice through the camera, 

 exposing one-half of the width on each passage. After processing, the film is slit to 

 give two lengths of the 8-mm. width, with perforations on only one side. In the 

 other case, the camera takes the film in the final 8-mm. width. The double-width 

 film has less tendency to give trouble from stretching of the wet film during processing. 



Identification of Cut Films. — Since it is often difficult to identify the emulsion sur- 

 face of cut films for proper loading into the film holder, cut films are usually supplied 

 with reference notches near one corner. When the notches are on the right side of the 

 top edge, the emulsion side of the film faces the operator. In addition, the number, 

 shapes, and arrangement of the notches are used to identify the type of emulsions as 



