Apple Aperture Digital Photography Fundamentals - Manual (Page 23)

Chapter 1 How Digital Cameras Capture Images 23
You can eliminate camera shake by using a tripod or by increasing the shutter speed to
a value higher than the focal length. For example, if you’re shooting at a focal length
equivalent to 100 mm, you should set your shutter speed to 1/100 of a second or faster.
The digital image sensor will capture the image before the movement of the lens has
time to register additional light information on the sensor.
Note: Some lenses have image stabilization features that allow the photographer to
shoot at a shutter speed whose value is lower than the focal length of the lens.
Minimizing Red-Eye in Your Photos
Red-eye is the phenomenon where people have glowing red eyes in photographs. This is
caused by the close proximity of the flash (especially built-in flash) to the camera lens,
which causes light from the subject to be reflected directly back at the camera. When the
flash fires, the light reflects off the blood in the capillaries in the back of the subject’s eyes
and back into the camera lens. People with blue eyes are particularly susceptible to the
red-eye phenomenon because they have less pigment to absorb the light.