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DUST AND NOISE
IMAGE DEVELOPMENT
Two factors are the “forever enemies” of image
quality: dust and noise. Dust spots on the image
result when material lands on the photosensor of a
camera or on film to be scanned. It is a serious
problem with SLRs as the debris is recorded on
every image. Noise—usually seen as pixels markedly
different to neighboring pixels and not caused by
subject features—arises from the electronic
properties of the photosensor of a camera or scanner.
Noise control
You can reduce noise where the noise has a higher
frequency than the image detail itself—in other
words, if the specks are much smaller than the detail
in the image. This is one advantage of increasing the
pixel count of images. In low-resolution images,
applying a noise filter smudges image information
along with the noise signals. Digital filters such as
Noise Ninja are effective at reducing noise only
where required, and all raw converters can reduce
noise. DxO Optics stands out by reducing noise
before applying color interpolation.
Dust on sensor
A 300 percent enlargement of
the corner of an image shows a
few faint specks of dust. They are
blurred because they lie some
distance above the sensor, which
“sees” only their shadows. However,
with manipulation, the pale spots
will become more visible.
Dust revealed
The full extent of the dust spots
is revealed when we apply an
adjustment layer to increase contrast
and decrease exposure of the image.
This presents the worst-case scenario
and makes it easy to identify and
eliminate the spots.
Dust removed
Use the Spot Healing Brush, Healing
Brush or Clone Stamp tool to remove
the dust spots. Set the brush to just
slightly larger than the average spot,
with a sharply defined brush edge,
and sweep systematically in
one direction.
Dust-removal options
Some scanners provide features to mask dust damage,
replacing the resulting gaps in the image with pixels
similar to those adjacent to the problem areas. These
can work well, although some may disturb the film’s
grain structure, while others work only on color film.
Many cameras incorporate mechanisms to
reduce dust, using, for example, rapid vibration to
shake off particles or antistatic coatings to avoid
attracting particles. Certain SLRs offer dust-removal
software: you photograph a plain surface, have the
result analyzed by the software, which then creates
a “mask” that can be applied to images to remove
the dust. You can also help the camera directly by
cleaning the sensor using ultrasoft microporous
swabs or ultrafine brushes that sweep up the dust
and reduce static charges.
Manual removal
The key image-repair technique is to replace the
dust with pixels that blend in with neighboring
pixels. Depending on your tool of choice, you either

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