Patent GB-572150-A (GB)
Title: Improvements in or relating to a device for testing a flashlamp synchronising mechanism for a photographic shutter
IPC: H05B41/32
Filed: 1943-08-26
Abstract: 572,150. Testing flash-lamp synchronizing mechanism. KODAK, Ltd. Aug. 26, 1943, No. 13931. Convention date, Sept. 23, 1942. [Class 98 (i)] A device for testing flash-lamp synchronizing mechanism for a photographic shutter comprises a light-tight housing within which a support for a piece of light-sensitive paper is mounted for rotation by externally accessible means on the housing, one wall of which facing the sensitive surface of the paper is provided with two holes disposed on a line intersecting the axis of rotation of the support, so that when during rotation of the latter one hole is exposed directly to the light of a flashlamp situated in front of the apertured wall and the other hole is simultaneously exposed to the light through a shutter, the synchronizing mechanism of which is to be tested, two arcuate image traces are formed on the paper from which the performance of the mechanism can be determined. As shown, the tester comprises a light-tight housing 10 having a bottom section 11 and a telescoping cover 12. A paper support 13 on a shaft 14 is rotatable from outside section 11 by a knob 15, and has a central pin 17 on to which a light-sensitive sheet 16 may be impaled. The cover 12 has two small holes 18, 19. An adapter ring 20 concentric with hole 18 receives a removable lens board of a camera. A flashlamp is mounted in a socket associated with a battery case, and the lamp circuit is adapted to be closed in timed relation to the actuation of the camera shutter by the synchronizing means mounted on the camera lens board. After the shutter is set, the paper holder is spun by the knob 15 and the switch on the battery case closed with the flashlamp held in front of the tester. The paper is removed and developed, and by inspection of the two arcuate traces it can be determined whether or not the peak illumination of the lamp was included in the exposure and if the shutter was opened too early or too late: The exact peak of the lamp may be determined by observing the first point of the longer trace to appear during development. Alternatively, a very small hole 32 in line with holes 18, 19 may be arranged in the cover 12 to form a short trace corresponding only to the peak illumination. The hole 19 may be covered by a filter cutting out all light below an intensity value including the lamp peak. The holes 18 and 19 may be spaced at different distances from the centre and may be on the same side thereof. The hole 19 may be elongated radially of cover 12 and be covered by a filter graded continuously from a mininum nearer the centre of rotation to a maximum on the outside. The curved trace has a form corresponding to the characteristic time-light curve of the lamp. The hole 19 may be replaced by a hole of the form shown in Fig. 13. To avoid removal of the shutter assembly, the housing 10 may be placed against the open rear of a camera. Specification 508,074 is referred to. The Specification as open to inspection under Sect. 91 states also that the knob 15 may be replaced by a coupling connected to a constantspeed motor, and the tester used for determining shutter speed. This subject-matter does not appear in the Specification as accepted.