In the old time, shutter was a cap on lens. Later on, the opening was controlled by a drop shutter. It was a sheet of wood about three times the diameter of the lens in length and a wider than diameter width. The center part of the sheet had an opening. It was locked with it bottom part covering the lens. After unlocking, the sheet dropped down. Light would enter the lens for exposure when its middle part pass through the lens and stopped exposure when it reached the end of its dropping with the top part covered the lens. There is a known problem, when the center part is a bit narrow with a moving or shaking subject; the final image would have a twisted, elongated or shortened effect. But a few smart photographers made use of this special effect, and had those without knowledge of this shutter astonished and supposed that effect might be a new invention.



If the subject moved when the drop shutter reached at its center potion, we might have a twisted, elongated, or shortened result. These images are not actual sample. We use them to show the consideration of such effects.

Even focal plane shutter can meet such kind of effect. No matter it moves from left to right or up to bottom, it may meet with fast gesture or movement of subject.

Besides exposure, shutter speed has an effect called freezing power. Freezing power is a relative effect between the subject movement and the shutter speed. High freezing power will have a rigid image, but with increased sharpness, low freezing power will have a lively image, but with decreased sharpness. From some obvious examples, this effect is easily understood and is easy to master. Effect is basically an individual choice, e.g. when taking sport photo, high freezing power can catch a motion screen, low freezing power can produce an active screen. It would be good if the effect matches the event.

Shutter speed can be taken as time of exposure; sensitive material (film) may have different result with different length of exposures. According to the specification of Kodak films, there is a range of exposure time with no adjustment required. The range is quite great for modern film, which normally ranged from 1/10000 sec. to 10 sec., exceeding general application. But when image quality is considered, it is better to keep a not too short exposure.