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Photography Question 
Christina M. Pontius

Shutter Speed Vs. Aperture

Besides controlling light, shutter speed also controls what?
Besides controlling light, an aperture also controls what?

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3/20/2007 11:45:46 AM

John H. Siskin
BetterPhoto Member
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Hi Christina,
Shutter speed records the way action is displayed. A long shutter speed smears action together, while a short shutter speed stops action.
The aperture controls the amount of area in sharp focus - which is called depth of field. If you focus at 5 feet from the camera, a large aperture will give you sharp focus at just 5 feet. If you took the same picture at a small aperture, you might be in focus from 4 feet to 7 feet, depending on your aperture.
You might want to look at my article for more information:
Photography Exposure Basics: Shutter Speed, Aperture, ISO
John Siskin

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3/20/2007 11:57:48 AM

Ken Henry   For Flash Photography you can control light by using aperture and use shutter speed for controlling ambient light(available light).

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3/28/2007 7:06:43 PM

Alan N. Marcus   Hi Christina,

The aperture is an opening in an optical system that restricts the passage of light. Since the opening is round it obeys the geometry of circles. Long ago it was decided that the increment of adjustment should be a doubling or halving i.e. 2x incremental change. To double or half the area of a circle its diameter is enlarged or reduced using a specific number set. The set is 1 1.4 2 - 2.8 4 -5.6 8 11 16 22 -32 45 64. Each number is its neighbor on the right multiplied by the square root of 2 which is 1.4 (rounded). Each number is its neighbor on the left divided by 1.4. These values are known as f/stops or simply stops, however the official name is focal ratio.

A secondary occurrence resulting from a change of aperture is a change in dept-of-field and depth-of-focus. As aperture size decreases, depth-of-field and depth-of-focus increase. A tiny opening nearing f/64, results in the depth-of-field approaches that of the pin-hole whereby everything is in focus. The sharpest setting for a lens is about two f/stops down from maximum. For most cameras this is about f/8. At larger apertures acuteness degrades as more of the periphery of the lens is utilized. This is true because light rays stemming from the lens edges require more bending (refraction) and therefore are more likely misdirected. At tiny apertures acuteness also degrades. This is true because a higher percentage of the light rays strike the edges of the aperture. As light rays pass close to a barrier they are misdirected, a phenomenon known as diffraction.

The shutter is a gate that allows light to play on the film or chip for a limited time. This is necessary as the light sensitive media (film and chip) accumulate light energy. The early shutter was simply a lens cover, removed and replaced by hand. The next innovation was an air operated shutter. A rubber bulb was squashed by hand. This sent air pressure to the shutter holding it in the open position. As long as the bulb was kept depressed, the shutter remained open. Modern shutters retain the B setting for bulb. Modern shutters are clock mechanisms. The 2x incremental change in duration remains in common usage. A typical time series is in seconds and fractions of a second thus: 4 2 - 1 1/2 - 1/4 - 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 -1/2000. Long shutter speeds require that the camera be securely mounted to prevent movement whereas at 1/30 the trained hand can hold the camera steady. Higher shutter speeds are required to arrest motion such as at a sporting event. Higher shutter speeds are also required to suppress camera movement when long lenses are employed.

The aperture and the shutter are the major controls used to manage exposure. They are worked together to achieve the desired level of exposure presented to the film or chip.

Alan Marcus

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3/28/2007 11:10:23 PM

Ariel Lepor
BetterPhoto Member Since: 9/8/2005
  I wrote something you might find of interest. Camera Settings

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3/28/2007 11:29:59 PM

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