Apple Aperture Digital Photography Fundamentals - Manual (Page 25)

Chapter 1 How Digital Cameras Capture Images 25
Reducing Digital Noise
Digital noise is the polka-dot effect in images with long exposures or images shot at
high ISO settings in low-light situations. The effect is most noticeable in images shot in
low-light situations. Many consider digital noise to be a synonym for film grain. Although
the causes are the same, the effects are quite different. Some film photographers
purposely shoot images with enhanced grain for artistic effect. However, digital noise
detracts from the image because of the sporadic bright pixels within solid colors, and
lacks the aesthetic qualities of enlarged film grain.
You can reduce digital noise by taking your photographs at ISO settings between 100
and 400. The 400 ISO setting provides more exposure latitude, but even 400 ISO
exhibits a little noticeable digital noise. If your subject is not moving and you can’t use
a flash, using a tripod can allow you to shoot successfully with low ISO settings.
Many DSLR models come with a noise-reduction feature. If you turn on the noise-
reduction feature, it is automatically activated when you shoot long exposures. The
camera color corrects at the pixel level, processing the image as it’s shot. The main
negative aspect to digital noise reduction on the camera is the significant lag time
required for the image to process between shots. One way to avoid this lag time
between shots is to keep the noise-reduction feature on your camera off and use the
Aperture Noise Reduction adjustment controls after you’ve imported your images.
100 ISO 200 ISO 400 ISO
800 ISO 1600 ISO 3200 ISO