SHUTTERS 



99 



Diaphragms are commonly of two types. The rotating disk shown in Fig. 4 is the 

 cheapest, but it does not provide a continuous series of lens openings and is bulky if 

 more than a few stops are to be used. The iris 

 diaphragm consists of a number of ring sectors, 



usually made of thin metal, which will be called / _ I __ \ /b 



"diaphragm leaves." Figure 5 shows the action of / ^^'^ — ! "^^^/^ 



a typical iris leaf. It has a pivot A at one end, the 



other end is provided with a stud or some similar 



Fig. 4. Fig. 5. 



Fig. 4. — Disk diaphragm of simple Kodak shutter. 



Fig. 5. — Action of a single diaphragm leaf (Julius Springer), a, fixed end of leaf on 



pivot; h, movable end of leaf at full opening; 6i, movable end of leaf at intermediate 

 position; 62, movable end of lead at smallest opening. 



fastening which is fitted into a short slot in a rotatable ring. Three different posi- 

 tions of the single leaf are shown in Fig. 5. Figure 6 shows how a seven-leaved 



Fig. 6 



I 2 3 



. — Action of seven-leaved iris diaphragm (Julius Springer). 1, full opening; 2, half 

 closed; 3, smallest opening. 



B 



a b c 



Fig. 7. — Complete iris-diaphragm assembly (Julius Springer), a, mounting plate, 

 6, leaves, 12 in all; c, slotted ring; d, iris opening indicator; e, iris ring connected to d\ j; 

 slot to limit rotation of ring; g, slot in which movable end of leaf is carried; h, stud that 

 pivots fixed end of leaf in mounting plate. 



diaphragm operates in the same three positions. The central lens opening can be 

 made larger or smaller by simple rotation of a slotted control ring in which the free 

 ends of all the leaves are fitted. 



