A SHORT GUIDE TO PHOTOGRAPHY
The lens aperture controls not only exposure, but also depth of field; the area between the closest object in focus and the furthest object in focus. The larger the aperture value, the greater the depth of field and the longer the shutter speed needed to make the exposure. The smaller the aperture value, the shallower the depth of field and the faster the shutter speed needed to make the exposure. Usually landscape photographs use a large depth of field (large aperture value) to keep the foreground and background in focus, and portraits use a shallow depth of field (small aperture value) to separate the subject from the background.
Depth of field also changes with focal length. The shorter the focal length, the greater the depth of field; the longer the focal length, the shallower the depth of field. Wide- angle lenses also create a strong perspective which gives a sense of depth in the image. Telephoto lenses compress the space between the subject and background and create a weak perspective.
The shutter controls not only exposure, but also the ability to stop motion. Fast shutter speeds are used in sport photography to stop action. Slow shutter speeds can be used to show the flow of motion such as water cascading over a waterfall. The use of a tripod is recommended with slow shutter speeds.
WHAT IS AN EV?
Ev stands for exposure value. A change of one Ev adjusts the exposure by a factor of two.
+2.0 Ev | 4X as much light |
+1.0 Ev | 2X as much light |
Calculated exposure | |
1/2 as much light | |
1/4 as much light | |
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A SHORT GUIDE TO PHOTOGRAPHY / 
