The Basics of Exposure:
There are three elements that factor into a photograph's exposure.
- ISO - the measure of a digital camera sensor’s sensitivity to light. In a film camera, the sensitivity of the film.
- Aperture - the size of the opening in the lens when a picture is taken.
- Shutter speed - the amount of time that the shutter is open.
Each of these elements relate to how light enters the camera. In order to take a perfect picture, one must have an understanding of the three elements of exposure. The intersection of these three elements determines the overall exposure.
A change in one of the elements will impact the effect of the others. When you adjust the shutter, you need to also adjust the aperture accordingly, and your last resort should be an adjustment to ISO as this is usually dependent upon specific lighting conditions.
Accurately gauging all of the elements in any given situation takes a lot of practice.
Here are just a few pictures showing what is possible when the photographer has the freedom to accentuate adjustments to these three variables:
Low aperture can blur an otherwise distracting background:
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| © www.digital-cameras-help.com |
Elevated ISO can shed some light on a dark night:
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| Photo Credit- Maddie Gregory |
High shutter speed can catch all the action:
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| Photo Credit- Kevin Kopanski |
That's a great article for beginners. I think a lot of photographers who are just getting started are easily confused by the three-variable approach to exposure. I don't think many people realize how night shots like the one you posted here are achieved using a slightly elevated ISO, or that indoor sports action is caught with a high aperture telephoto lens, so that quality isn't sacrificed at high shutter speeds.
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