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Grayscale images, desaturated process color images, over-saturated RGB images…they never seem
to mix well in a project. One way to tie a group of disparate images together is to create an overall color
scheme by applying specific colors to different points on a Grayscale tonal range. It sounds complicated,
but it’s easier than you think!
To duplicate the effects shown in this tutorial, I recommend you open fishing.jpg (available in the downloadable photoshopfix5.zip archive). The archive also contains colorscheme.psd, a sample file of color chips. If
the colors are too extreme for your
taste, choose Hue/Saturation, and
lower Saturation. Be sure to use the
Info palette to properly set their
Grayscale percentages.
First, set the colors for the 100%, 75%,
50%, 25%, and 0% values of a Grayscale
tonal range. To do this, create an RGB
document at 300 x 600 pixels, and fill the
Background layer with 50% Gray (Edit >
Fill > Contents). Add a new layer, create
a box at the top with the rectangular
marquee tool, and click the Foreground
Color swatch in the toolbox. In the resulting
Color Picker dialog box, enter the
black RGB values from the image below,
and press Option-Delete (Alt-Backspace)
to fill the selection. Create another box
below the black one, and repeat the
process to fill it with the dark green RGB
values from the image. Continue
this method until you have five boxes
filled with black, dark green, blue, light
cyan, and white respectively.
Make sure everything is deselected
(Command/Ctrl-D), open the Info palette
(F8), and choose Palette Options from
the palette menu. Set First Color Readout
to Grayscale so the palette’s first display
will be the Grayscale value of the pixels
under your cursor. In your file, make a
rectangular selection of the dark green
chip, and press Command/Ctrl-U to
access Hue/Saturation. Place your cursor
over the dark green chip, and you’ll
notice the Grayscale value (K) in the Info
palette is not quite at the 75% threequarter
tone. Drag the Lightness slider
until the second number of the Grayscale
value reads 75% when your cursor is
over the color chip. Click OK to apply it,
deselect, and do the same for the blue
(50%) and light cyan (25%) chips until
you’ve adjusted them to their designated
Grayscale percentages in the Info palette.
 
Open the grayscale fishing.jpg
image, and choose Image > Mode > Indexed
Color to tie image values to those
in a color lookup table. Position the color
chip file you created and the fishing image
side by side. With the fishing image
selected, choose Image > Mode > Color
Table–this is where the magic happens.
Click and drag your cursor through the
first four rows of the Color Table. When
you release the cursor, the Color Picker
appears asking you to select the first
color. Click on the black (100%) chip in
the other file and Click OK in the Color
Picker. The Picker returns asking you to
select the last color. Click on the dark
green (75%) chip, and click OK again. The
Color Picker disappears, and you’ve redefined the first quarter of the Color Table.
Drag your cursor through the next
four rows in the Color Table. Click on the
dark green (75%) chip to select the first
color, then the blue (50%) chip to select
the last color. After selecting the next
four rows, choose blue as the first color
and light cyan (25%) as the last color. For
the bottom four rows, select light cyan
as the first color, and white (0%) as the
last color. Notice during this process, the
fishing image updates, and while it may
look strange at first, it looks fantastic after
you set the last quarter of the Color Table.
Choose Image > Mode > RGB Color, and
convert the image back to RGB. The final effect is shown below.
Keep in mind Indexed Color mode
restricts images to 256 colors. That’s
not a problem for this fishing image,
but it can cause banding in images
with regions of graduated shades.
Extreme color shifts can create
banding in large, flat areas such as
a sky. If you get banding, apply the
Add Noise filter after converting
back to RGB or CMYK.
By making the first and last colors
the same in each quarter range of
selected rows in the Color Table,
you can posterize an image with
a high level of control. Not only
does it define exactly what colors
are used, but it also defines which
intermediate shades those colors
are employed through.
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Simon Tuckett is an illustrator and
retoucher in Toronto. For more information,
visit www.simontuckett.com. This article is excerpted from Photoshop Fix, Volume 2, Number 2, and is reprinted here by permission. Copyright ©2005, Dynamic Graphics, Inc. All rights reserved. For a free trial issue, visit Photoshop Fix online.
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