Specifications
The Digital Fine Print Course
Editing a Fine Print
Reducing Noise and Artifacts in Scanned Images
A digital print from a scanned negative will often exhibit a more granular image structure
compared with an RA4 optical-chemical photographic print enlarged directly from the
same negative. These artifacts appear in proportion to the film’s density. It therefore tends
to not be as significant a problem with scanned transparencies whose reversed densities
effectively ‘hide’ these artifacts in the shadows. Excessive artifacts are also often only
present in the ‘unwanted colour’ in the affected area of the image. For example skin tone
artifacts are often only visible in the green and blue channels (G + B = Cyan). The follow-
ing methods will variously help to reduce artifacts in digital files.
Copyright Les Walkling 2012
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Apply the Surface Blur filter to the affected channel(s). Selections can also be used to
further refine the correction through the local application of varying degrees of blur.
Use the smallest Surface Blur pixel radius that minimises the local artifacts. Then sub-
tly sharpen any unaffected channels. This technique will help preserve the overall pho-
tographic appearance of the image while reducing some unwanted artifacts.
Applying the Dust and Scratches filter at a very small pixel radius to a duplicated
image layer blended with Darken mode ensures only the minute areas of lighter tone
within the unwanted granularity are replaced by the blurred and darkened areas of the
filtered layer. A layer mask based on a Find Edges filtered copy of the image will help
preserve edge detail while minimising all over granularity.
A more sophisticated method applies the Dust and Scratches filter to a copy of the
most artifacted channel(s), which is then blended with the original channel(s) using the
Darken mode via the Apply Image tool (File>Adjust>Apply Image).
Fill a layer with paint whose colour has been sampled from the image areas that
require the most smoothing or reduction of granularity. This paint layer can be filtered
with the Noise filter at a small pixel radius that approximates the granularity of the
photographic image itself, and is then blended at a low opacity (typically 20% to 50%)
using the Darken blending mode to help smooth out excessive granularity.
Sometimes small degrees of lossy JPEG compression can appear to reduce scanner
(and digital camera) artifacts by reducing the effective variance between different pix-
els, thereby smoothing out local values, especially in areas like skin.
Nikon scanning software incorporates a GEM function and SilverFast uses a GANE fil-
ter that significantly reduce grain and artifacts in the scanned image. On close inspec-
tion individual colour channels can become locally posterized especially in smooth
toned areas, though these effects are usually only visible in giant enlargements.
Software like NeatImage™ or Noise Ninja™ will significantly reduce digital noise, and
scanner specifc ‘grain profile’ can be created for repeated use or batch processing.
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