Basically, there are two main types of shutter: those that work inside or just behind the lens, known as between lens shutters, including sector shutters; and focal plane shutters, which are positioned close to the film.
The between lens shutter closely resembles the aperture and is positioned between the lens elements, near the aperture blades. It is made up of two or more overlapping metal blades. which spring open for the time of the exposure and then close again. These shutters are very light and compact, and can synchronize with flash at all speeds. But between lens shutters have two drawbacks: few work at speeds of over 1/500, and they are costly to produce for cameras with interchangeable lenses. This is because each lens requires its own integral shutter and a separate means to block light from the film when the lens is removed.
Between lens shutters are used mainly on rangefinder 35mm cameras and roll film cameras. Read the rest of this entry »
The speed control on this type of mixer results from the interaction of mechanical action and electronic control. Two variations of electrical control can be found but each uses the same mechanical action.
Two small spring steel plates are fixed to the cooling fan on the lower end of the armature shaft. They are slightly bowed and joined at either end by a small weight. Only the top plate is secured to the fan and shaft. When the motor rotates, the weights on each end of the joined plates are forced outwards by centrifugal force. As they are formed in a bowed configuration and joined at either end, the outward movement of the weights causes the lower plate to be forced downwards. The degree of movement is proportional to the rotational speed of the armature. This movement is used to actuate a switch on the speed control panel. Read the rest of this entry »
There are two main types of shavers: fully portable (powered by batteries, either dry cell or nickel cadmium rechargeable), and mains powered which usually incorporate a variable voltage option switch (110-130 volts or 210-240 volts). Correct maintenance is essential if they are to work efficiently and have a long and useful life while simple care and cleaning will greatly improve their smooth operation and reduce the likelihood of recurrent breakdowns. Read the rest of this entry »
