Highest Quality Capture: Workflow Phase I - Black and White in Photoshop CS4 and Photoshop Lightroom - page 70

The image on the previous page was captured on i lm in a low light
situation with 400 ISO i lm pushed to 1600. The grainy structure of the
image illustrates a quality of i lm that often added to the mood and
feel of a print.

The image of the boys running (right) was digitally captured at 1/10
of a second with an ISO setting of 400. With digital capture, noise and
grain appear very similar, although shadow areas tend to have a more
blotchy look with digital noise. Noise in color images tends to have a
more magenta-green look. (See image above.)

Digital color noise

The digital camera's sensor measures light for each pixel and creates
a matrix of pixels that represent the image. The sensor itself carries
a certain amount of noise inherently; however, in most lighting
conditions, the light is signii cantly stronger than the inherent camera
noise. In more extreme conditions where the light is low, or when a
higher ISO setting is needed, the noise levels typically increase and
produce more abrupt and jagged pixels with a Christmas-colored
pattern of red and green. This occurs because there is more noise data
than light data available to the sensor.