MOTION-PICTURE PHOTOGRAPHY 



683 



shown), a dial and control handle are provided for the latter. Dissolves and fades 

 may be made in the camera manually or automatically, the light being cut off or 

 increased by variation in the angular opening of the shutter. These operations are 

 more commonly done in the optical printer (see Process Photography). The prismatic 

 magnifier used for focusing is just in back of the slot provided for focusing vignettes, 

 and above the latter there is an exposure indicator plate. In focusing it is also possible 

 to use an attachment, not shown in Fig. 25, whereby the film is used as a focusing 

 screen, the image being viewed from the back by transmitted light. 



On the left side of the camera (Fig. 26) the view finder is mounted. This 

 is equipped with mattes corresponding to the various lenses commonly used, defining 

 the field for each lens. This photograph 

 also shows a combination sunshade, matte 

 box, gauze carrier for diffusing purposes, 

 filter carrier, vignette holder, and an iris for 

 irising in or out on any desired part of the 

 picture. 



An interesting camera of recent design 

 is the Twentieth Century silent model 

 shown in Fig. 27, developed at the Twentieth 

 Century-Fox Film studio in Hollywood. 

 To date this appears to be the only camera 

 of domestic origin which may be used on 

 sound stages under normal conditions with- 

 out some form of "blimp" or sound-insulat- 

 ing covering. The mechanism has been 

 silenced to a degree where the cylindrical 

 housing itself provides sufficient insulation. 

 The motor of this camera drives direct to 

 the shutter. The speed with which the film 

 is moved from frame to frame has been 

 reduced by about 20 per cent, the accelera- 

 tion is uniform, and the dwell time is so long 

 that a 200° shutter opening may be employ- 

 ed. At the moment of engagement and 

 disengagement the take-down pins have no 

 vertical movement and go straight in and 



out of the perforations. All parts are sealed against dirt, sand, and water. The 

 lens-focusing scale is uniform for any focal-length lens, and by means of a special 

 optical design incorporating automatic correction for focus and parallax, the view- 

 finder image always conforms to the image on the film. 



In newsreel work small portable 35-mm. silent cameras are often used. These 

 may be mounted on a tripod, as shown in Fig. 28, or held in the hands. Some types 

 have a single lens, usually of 50-mm. size and speed //2. 5; others carry a three-lens 

 turret. They are driven by a hand crank, spring motor, or, less often, by an electric 

 motor. 



Motion-picture lenses are usuall,y of large aperture, ranging to a maximum of 

 //1. 3 in some sizes. The most frequently used focal lengths are between 25 mm. 

 (1 in.) to 100 mm. (4 in.), although sizes up to 200 mm. are often kept on hand. The 

 bulk of the work is usually done with 40-, 50-, and 75-mm. lenses of about //2.0 speed. 



Advances in motion-picture lens design have followed progress in the manufacture 

 of film. As long as motion-picture films were sensitive mainly in the blue region, 

 lenses were generally constructed to accurate focus for the blue F and yellow D Fraun- 



FiG. 28.— Hand camera {Bell & Howell). 



