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To prevent print-through from print on the back of pictures in magazines
I always place a sheet of matt black card behind the page. This makes the
print on the back practically disappear and improves the resultant scan
no end.
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When scanning pictures I have found that it is really a matter of trial
and error to come up with the best result
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Magazine pictures are a problem because of their dot pattern (half-toning)
which tends to produce patterns in the final result (aliasing) - to overcome
this I try different resolutions until the picture looks best at
the final size
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Aliasing occurs when the frequency of the half-tone pattern is greater
than half the sampling frequency
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The scanned picture will contain a lower frequency interference pattern
caused by scanning at insufficient resolution to resolve the finer detail
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One good tip is to scan at 300dpi or higher, apply a median filter and
sample down to a smaller picture size
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Some software (de-screen option) that comes with scanners does a good job
of avoiding this pattern effect
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I select the area to be scanned after pre-scanning and then do the scan
at 300dpi
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This gives a very big file which I then reduce in Paint Shop Pro to about
800 pixels high using the "percent method" and including the "maintain
aspect ratio" option
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The Smart size option of Resize does a good job of maintaining quality
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It's also a good idea to check the histogram to make sure black is black
and white is white - if not stretch the histogram
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It is best not to increase the size of images - this tends to lose quality
more than reducing the size, although the Smart size option does a good
job here as well
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Large images can be scanned at 120 pixels/inch right off most of the time
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96-120 pixels is the resolution of most good monitors these days, so its
no use using a better resolution for pictures that will be used for viewing
only
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I find with my scanner that I have to set the contrast, brightness and
gamma levels to higher than normal as pre-sets
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I use +30 for brightness and +10 for contrast with gamma set to 1.6
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This means that my scans come out about the right density and balance and
there is little need to adjust things
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However, sometimes I have to crop the image or adjust the colour balance
or saturation for best effect
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If you want to print the scanned image 150 pixels/inch is a good level,
as laser and ink-jet printers have about this resolution
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After scanning I resample larger pictures to give a height of 800 pixels
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This gives image sizes of about 50-100k
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After adjusting the image size and other fine tuning details such as gamma
and brightness/contrast, I use the "unsharp mask" to give the image better
crispness
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I have found that if I save my jpgs again using "save as" they sometimes
just about half in file size due to the compression that occurs with jpg
images
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