Patent GB-191407787-A (GB)
Title: Improvements in Photographic Shutters.
Inventor: HEREWARD LESTER COOKE
IPC: G03B9/22
Filed: 1914-03-27
Granted: 1900-01-01
Abstract: 7787. Cooke, H. L. April 16, 1913, [Convention date]. Void. [Published under Section 91 of the Act.] Shutters with pivoting blades.-A photographic shutter is provided with three logarithmic scales for diaphragm, speed, and light-intensity values, as shown in Fig. 1. The setting-arm 67 carries two pointers 47, 66 travelling over two of the scales. The arm 61 for setting the diaphragm is adjustable by means of the pins 74 and slot 73 relatively to the plate 60 carrying the light-intensity scale 65. In the first instance, the correct exposure is given to a standard plate under a standard source of light by trial. The arm 67 is set so that the pointer 47 points to the exposure given. The arm 61 is set so that the pointer 59 indicates the diaphragm used. The screws 74 are loosened and the plate 60 adjusted so that the pointer 66 on the arm 67 points to the unit mark on the scale 65 indicated by the circle and arrow. The screws 74 are then tightened and the shutter is standardized for the particular plate. If, for example, the light intensity for exposure at any time is “-standard strength, the speed and diaphragm regulators 67, 59 are set correctly for exposure when the pointer 66 is opposite the graduation “ in the scale 65. This adjustment of the pointer 66 to the figure “ on the scale 65 is produced either by an adjustment of the speed pointer 47 to give four times the former exposure, or by adjusting the pointer 59 to reduce the diaphragm to four times the previous value, or by a combination of adjustments of the pointers 47 and 59 so that the product of the diaphragm opening and the speed is four times the previous product. To set the shutter for a plate having a speed N times that of the standard plate, the pointer 66 is brought opposite the graduation 1 on the scale 65 and, keeping the speed and diaphragm regulators 67, 61 fixed, the face ring 60 is adjusted by loosening the screws 74 until the pointer 66 is opposite the graduation <1>/N on the scale 65. For time or bulb exposures, when the time of exposure has been indicated by the pointer 47, the regulator 67 is moved over behind the plate 70 to set the shutter for a bulb or time exposure, and the exposure is timed according to the time previously indicated. The shutter is provided with a finger release 23 and with the usual pneumatic or other release mechanism. The manner in which the regulator 67 controls the speed mechanism of the shutter is shown in Fig. 3. The regulator 47 is integral with an arm 45 forming part of the plate comprising a rotating collar 43 and a slotted arm 44<1>. The slotted arm 44<1> acts on the speed-controlling arm 38 of the shutter by a pin 42 on a pivoted blade 39 and travelling in the slot 44. The plate 39 is pivoted at 40 to the shutter casing and carries a pin 41 which directly controls the arm 38. The portion 44<a>-44<b> of the slot 44, which is operative for instantaneous exposures, is determined by trial, as described in the Specification, to obtain the logarithmic speed scale 49. The portion 44<a>-44<c> of the slot, which is operative for time exposures, is concentric with the exposure and diaphragm apertures. The diaphragm aperture is formed by a number of leaves 50, shown dotted in Fig. 9, each leaf being pivoted on a pivot 51 and carrying a pin 54. The pins 54 engage slots 55 in a plate 52 which is revolved by the diaphragm regulator 61. The shape of the slots 55 is also obtained by trial, as described in the Specification, to obtain the logarithmic diaphragm scale 64<a>.