Question by Jane: What is the length of time the shutter speeds represent?
shutter speeds are: B, 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000.
Choose four settings and say how you would use them for different effects in your photographs.
What is meant by a focal plane shutter in a 35mm slr camera?
Best answer:
Answer by monophoto
Shutter speeds are in fractions of a second – 1 = 1 sec, 2 = 1/2 sec, 4 = 1/4 sec, etc. B stands for “bulb” and means that the shutter will be open for as long as you press the shutter release. It is intended for use with a flash where the length of the exposure is determined by the duration of the flash and not by how long the shutter is open.
The choice of length of shutter speed is used to accomplish two things. One is to use it, in conjunction with the aperture setting, to control the exposure on the film or digital sensor. The other use is to control how the shutter captures motion. A slow shutter speed (eg, 1/2 sec) will show a moving subject as a blur, while a fast shutter speed (1/2000) will ‘freeze’ the subject motion.
The earliest shutters opened and closed all at once – the aperture blades would move in a way that caused the diameter of the roughly circular aperture to increase and then decrease. When SLRs came along, there was an opportunity for a focal plane shutter in which a curtain containing an opening of a given dimension would move across the image frame in front of the film (or today, the digital sensor). The combination of the speed at which this curtain moved, and the width of the opening in the curtain, determined the effective shutter speed.
There are two general kinds of focal plane shutters. The earliest shutters moved horizontally – basically, along the long dimension of the 35mm frame. Manufacturers eventually mastered the technology of making the shutter curtain move vertically which provided the opportunity to achieve higher shutter speeds.
One of the quirks of the focal plane shutter is that the exposure takes place at distinctly different instants of time at different point on the frame. As a result, it is possible for a focal plane shutter to actually introduce distortion if the subject is moving at the time of the exposure. For example, if the subject is moving in a direction that is opposite to the direction of motion of the shutter curtain, the image will actually be foreshortened.
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