is accomplished automatically.

Abstract The description of the general outline and the main performances of the ZDF-50 type waiting framing camera is given in this paper* The waiting operation of the camera is £>ased on the triangular mirror which is drived by a motor. The framing rate is 5x1 CK pic­ tures/sec at a rotor speed of 1500 rps. A circuit can record 110 frames with a frame size of 10x18 mm* The relative aperture at the film is about f/19« The dynamic photographic resolution is from 22 to 25 Ip/mm.The framing lens consists of a doublet and a meniscus element. There are two objec­ tives, each of them is suitable for using in the field and in the laboratory respectively, and three forms of shutters: electromagnetic shutter, fast open shutter and blast shutter. The rotating mirror house of the camera is vacuumized.A transistor circuit and digital display are incorporated into the control system of the camera. The operation of the instrument is accomplished automatically.Lastly, the detonator exploding pictures taken by this camera are presented.IntroductionZDF-50 rotating mirror framing camera with fast opening shutter, adjustable framing lenses and motor driving is an universal photographic instrument which can be used for investigating lots of fast phenomena. Owing to the rather large relative aperture and fairly good image quality, the recording result is satisfying.Overall designWaiting mode scanning systemA continuously operating mirror scanning system may be formed in manifold way. We syn­ thesized various factors, and decided to adopt a triangular mirror and two optical straight inlets arranged in one plane. (See Figure 1.T Two inlets and two working angles are marked by 1,2 and 1*,2* respectively. The optical axes of two channels are parallel each other, but their directions are opposite and both of them perpendicular to the mirror's rotation axis.Figure 1, Waiting mode scanningsystem. Figure 2. Basic optical system diagram of the camera.