Maybe your scanning program
has an option to select a varying amount of 'sharpening'. Mine
allows for a choice between None, Low, Medium, High and Extreme.
Even if your scanning capture
program doesn't have this option, maybe your image processing program
While you might think it
best not to 'alter' your scan at all, and therefore to leave sharpening
set to 'None', this is not the case. With most scanners costing less
than $10,000, there is inevitably a certain amount of blurring caused by
the mechanical movement of the scanning mechanism, and an appropriate
amount of sharpening can compensate for this.
Here are five images
showing the same 600 dpi scan with the varying levels of sharpening
offered in my scanning software.
Notice how the fine details such as torn paper fibers around the
perforations, line detail in the image, and background detail on the black
background are all fuzzy and indistinct.
Low sharpening. There
is a huge difference between this and no sharpening. You can now see
individual pieces of fiber and lines of detail, and can make out some
background texture as well.
Even more detail, and both the background and the paper surface is now
appearing much more textured.
Maybe a little more detail, but not much difference to the medium setting.
Very little difference to high sharpening.
I usually settle for a
'medium' setting - because I can't see much more detail in the high or
extreme, I'd rather not risk upsetting other aspects of the total scan by
using more of the sharpening than is needed. You should choose what
is best for your scanner, choosing both a test image like this one and
also a high quality color one as well to make sure you're not losing some
of the finer detail in color change at the higher sharpening settings.
Maybe your scanning
software doesn't have a sharpening adjustment. Or maybe it isn't a
very good adjustment and degrades the image in other ways when it is used.
In that case, perhaps you have a sharpening option in your image editing
program. I use Adobe's Photoshop, which is generally considered to
be the very best image editing program there is, but which is also, alas,
not very 'user friendly' and also quite expensive. However,
increasingly, other less fully featured editing programs are getting more
and more intelligence, with the main difference being that the more
consumer oriented programs have very much friendly user interfaces, and so
the chances are that you have some type of sharpening option in your
Photoshop offers four
different sharpening options. The 'best' method is what it calls,
strangely enough, 'unsharpen mask' - you might think that this, well,
unsharpens an image, but, no, you'd be wrong - it sharpens it (remember
what I said about it not being very user friendly!). If your program
offers this unsharpen mask function, then you should use it in preference
to any other sharpening functions.
Here first is the
unsharpened image and then the same image after being processed by the
standard 'sharpen' filter in Photoshop.
There is a definite
improvement, but overall it isn't as clear as the 'Low' setting on the
By comparison, here is the
image after using the unsharpen mask filter.
This is maybe a bit
better than the regular sharpen filter, and perhaps comparable with low
sharpening from the scanner, but still not as good as medium sharpening.
One of the strengths
of the unsharpen mask is that you can adjust its settings, depending on
the image and the degree of sharpening needed. I typically use
50-80% sharpening, a radius of 2 pixels and a threshold of 4-5 levels.
To summarize this section,
you should always add some sharpening to your scans. Usually you can
get best results by using the sharpening function in your scanning
software, but if this is not available or does not give a good result, use
a sharpen function in your image editing software - preferably an
unsharpen mask if it is available, otherwise, whatever else makes a
visible improvement to your scan.