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A great way to save on your printing costs is to
use two inks instead of four. You can also produce some
incredibly striking images, and some cool effects, for print,
Web, and artistic purposes. But which color mode is right for
your project, Duotone or Multichannel? Let's do a comparison.
Duotone color mode takes a grayscale image and
adds an accent color. If you're starting with CMYK or RGB,
you'll have to use the command Image> Mode> Grayscale first. You
can then access Image> Mode> Duotone. Duotone, by the way, is
sometimes used as a generic term that also covers monotone (one
color), tritone (three colors), and quadtone (four colors). You
choose your colors in the Duotone dialog box.
By clicking on a color swatch you open the Color
Picker. Typically when creating a Duotone, you'll find using
Custom colors simpler. When the Color Picker opens, click on the
Custom button. Select the type of ink from the pop-up menu
(dependent, of course, on your print job's specs), and choose a
color. In this example, we'll create a sepia look by using
Pantone Process Yellow. (To the left of the color swatch is the
Duotone Curve button. We'll explore what you can do with this
option later.) The Overprint Colors button at the bottom is used
primarily with tritons and quadtone images. It gives you
control, to some degree, over how inks will interact. Note that
you can re-open the Duotone dialog box at any time to make
changes by simply using the command Image> Mode> Duotone.
When we compare the grayscale and duotone
images, you can see that Photoshop has changed the hue of all
the pixels, rather than perhaps just adding some colored
accents.
Let's look a little more closely, using Color
Samplers and the Info palette.
When comparing the two Info palettes, notice
first that the duotone's color values are shown as "1" and "2,"
which represents the inks selected in the Duotone dialog box.
Next, notice that the black percentages for each spot are
unchanged – Photoshop simply added an equal amount of the second
color to the pixel's color value.
Now let's look at the Channels palette to see
what a duotone is actually all about.
You'll see that there is but a single channel,
despite the fact that we're using two colors in the image. In
Photoshop, rather than controlling the placement of ink by
editing a color channel, we use the Duotone Curves dialog box
(mentioned earlier). Open the dialog box by using the menu
command Image> Mode> Duotone, then clicking on the box to the
far left of the ink you want to edit.
If you work with Photoshop's Curves adjustment
(Image> Adjust> Curves), this box will look somewhat familiar.
The diagonal line represents how much ink will be placed at
given color values. Think of it as a grayscale continuum,
ranging from white to black. By default, the ink is distributed
proportionally for each pixel value, from 0% to 100%.
You can change values by clicking and dragging
on the line or by entering numbers in the fields. Let's see what
happens when we make some adjustments.
As you can tell, you have a great deal of
control over how the ink is distributed according to pixel
value. Re-opening the Info palette shows what actually happens
to the pixels' colors.
Notice that Ink #2 (black) remains unchanged.
The first ink, however, is altered in direct relationship
between the percentage specified in the Info palette and the
value you assign in the curve. The percentage of ink shown in
the Info palette corresponds directly to the percentage in the
curve.
One further note on the construction of
duotones: You are not limited to "black and another color." You
can use any two colors you desire.
You can also extend the tonality of a grayscale
image by using black and a supplemental gray ink
Note that Photoshop let's you save duotone
images in a limited number of file formats.
In Round 2 of this battle, we'll explore the
Multichannel color mode. |