Weird distortion effect when moving (X-T100 & 50mm f2)

Started 2 months ago | Questions thread
A Marcus Forum Member • Posts: 50
Re: Weird distortion effect when moving (X-T100 & 50mm f2)

There are two mechanical shutter designs. Each have advantages and advantages. The between-the-lens shutter was popular; it uses metal leaves that overlap. When the go-button is pressed, the leaves open from the center. In other words, the opening starts out as a tiny hole and then expands to full open. After a dwell time, the shutter closes, the hole shrinks to a tiny opening and then closes. These between-the-lens shutters have an escape movement exactly like a spring operated pocket watch. They were the industry standard. However, they are only about 60% efficient because they open and close from tiny too large. In effect the run up and down the f-numbers as they operate. Because of mechanical limitation their top speed is about 1/500 second (some went to 1/800). Also, because of mechanical limitations, when a flash is used, it is difficult to cause the flash to work with the shutter (synchronization).

To solve the limitations of the between-the-lens shutter, the focal plane shutter was invented. This is a spring loaded curtain that hovers just over the film / digital sensor. When the go button is pressed, the curtain moves from one side of the camera to the other. The travel time is quite long. Good thing, the shutter speed is not the travel time. The shutter speed is the time it takes of a narrow slit in the curtain to move a short distance, its width. Such a design can permit shutter speeds in excess of 1/1000 of a second. The different shutter speeds are accomplished by adjusting the slit width. This design is even more difficult to synchronize a flash with the shutter slit opening. The chief advantages are high speed shutter and the fact that the shutter is inside the camera so interchangeable lenses need not have a shutter (price).

The chief disadvantage of the focal plane design is: The time needed to move the shutter from one side of the camera to the other is surpassingly long. If the camera is moved or the subject moves matching the slit travel, distortion will result. I once photographed a football game, the ball moved with the shutter slit, the players were frozen, the ball imaged super elongated.

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