Need for speed
By Adrian Toon, director of a2n.
Following on from last month’s column, where we looked at ƒ, this month we look at shutter speed.
Speed really refers to the time that a camera shutter is open, the shorter time that it is open, the ‘faster’ the speed. But a fast speed allows less light to fall on the sensor, so it ‘sees’ less of the light forming the picture. If we then couple this with ƒ and obtain a wide aperture, say ƒ2.0 or bigger (smaller ƒ number) we can maximise the light hitting the sensor given the higher shutter speed.
Why is it important? A slow speed could allow for camera movement while the picture is taken and cause blur across the image, known as ‘camera shake’. A fast speed will freeze any moving image reducing or eliminating any blur. Being creative, photographers can use this knowledge to their advantage to blur certain parts of the image for dramatic of creative effects.
Using the ƒ ‘stops’ on a camera, (eg, ƒ/2, ƒ/2.8, ƒ/4, ƒ/5.6, ƒ/8, ƒ/11 and ƒ/16) and the speed stops (eg, 1/30th, 1/60th, 1/125th, 1/250th, 1/500th, 1/1000th and 1/2000th of a second) these are perfectly placed so that moving one ‘stop’ on either scale offers the same exposure.
For example, 1/30th at ƒ/16, 1/60th at ƒ/8 and 1/125th at ƒ/5.6 all offer the same sensor exposure, but offer you different creative effects in your pictures.
Next month we will look at sensor speed as the third element of picture exposure.