There are two different methods to achieving
solid, pure, Black-Versus-White line art. One
is the Levels adjustment tool, the other is
Threshold. I’ll describe Levels first,
as it’s the one I would recommend when
working with pencil lines.
The Levels tool is located under Image -->
Adjustments --> Levels (or just hit CTRL-L).
You get a little window with some sliders and
what’s called a “Histogram”.
It displays the concentration of pixels in the
image. Looking at our histogram (Fig.
1), there’s a huge spike representing
all our light-grey pixels (the blank space on
the page) and a small hump of dark-grey pixels
(the line work). There are no pure white or
pure black pixels. What we really want is a
whole load of pure white pixels, some pure black
pixels, and a couple inbetween representing
the aliasing (softness) around the edges of
the lines.
The solution is simple – drag the little
White and Black arrows towards the center of
the histogram (Fig. 2) and
watch the greyness disappear. When the white
looks white, click “OK” to apply
the changes. While you’re experimenting,
you can hold ALT
to reveal the “Reset” button, which
will put the settings where they were when you
opened the tool.
If we open the Levels tool after having applied
our changes (Fig. 3), we see
that the histogram has changed to show that
there are now mostly white pixels in our image,
with a bunch of black pixels and a scattering
of dark grey ones. Excellent.
Using the Threshold tool (Image --> Adjustments
--> Threshold) achieves a similar effect
by simply making your image consist of either
black or white pixels (Fig. 4).
You can drag the slider back and forth to adjust
the effect. Using the space,
CTRL, and ALT
keys will allow you to pan around your image
and zoom in and out in order to get an idea
of how your image is being affected.
If you zoom all the way in to a Threshold-ed
image, you’ll see the jagged opposition
of black and white pixels. It may seem crude
and very late-eighties, but if your image is
set to 300 DPI, when you print the image out
you’re not going to see any of those jaggies,
just nice, very crisp lines. I recommend using
Threshold with images that have been inked.
Results with pencil can be sketchy (so to speak)
unless the line’s very clean and consistent.
I didn’t like the effect Threshold had
on my sketchy pencil clean-up job, so I stuck
with the results that Levels gave me. At this
point I set myself up with the default black
foreground and white background colours (hit
D), a nine-point,
variable-width solid brush and a similar eraser
(mapped to the eraser end of my Wacom pen, as
it is be default). Then I go in and clean up
the spots where I did a particularly heinous
job in the first place. With practice, it can
be quite easy to get along with a Wacom pen,
and I find this method of working to be productive.
A large tablet helps, too.
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