Single-Lens Reflex Camera

Image is reflected to the eyepiece by a movable mirror

All cameras have at least two ways to control light: the shutter and aperture. The aperture is like and iris in the eye, and controls light by changing size. When a photographer takes a picture, the shutter opens briefly and the image is exposed.

Lens Aperture

There are three different kinds of shutters used in digital cameras-leaf, electronic, and focal plane. Leaf and focal plane shutters are both mechanical and have moving parts-leaves or curtains.

Shutter Speed Shutter speed is usually expressed as a fraction – 1/2, 1/4, 1/30, 1/60, etc. Some professional cameras go as high as 1/2000, or even higher. A shutter speed of 1/4 means that the shutter is in the open stage for a period of one quarter of a second. A shutter speed of 1/2000 means it is open for only one two thousandth of a second. The longer the shutter is open, the more light is hitting the sensor. Shutter also affects motion blur. Slow Shutter for motion blur. Fast Shutter for stop action.

Shutter Speed Fast Shutter Speed Slow Shutter Speed Landscape photographers could try using a slow shutter speed on a waterfall. That gushing water will turn into a lava-like flow of fluid (above right). Go for a fast shutter speed and it will turn almost icy with splash caught frozen in mid air (above left). A slow shutter speed, used to make the waterfall deliberately blurred, has is more aesthetically pleasing.

When taking pictures in dark surroundings, indoors or outdoors, keep an eye on the shutter speed. If the selected focal length is 60mm the “safe” shutter speed should would be 1/60sec (one sixtieth of a second). If the selected focal length is 150mm than the slowest shutter speed should be 1/150sec. A slower shutter speed will generally cause a blurred image. Another way to reduce the needed light for correct exposure is by selecting a higher ISO setting, thus increasing the shutter speed.

ISO Speed

ISO speed 1600 without a tripod