Photography: Capture to Presentation, 2nd Edition Page 421 (421 of 672)

421
Making a Monochrome Conversion Using the Channel Mixer
1. Open the image you wish to convert.
2. Click on Image Adjustments Channel Mixer. Select the Monochrome check box at the lower-left corner
of the Channel Mixer dialog.
3. Try different combinations of the channel sliders
while observing the effect on the monochrome
image,
Figure 15-39.
The percentages usually
should add up to 100, although a higher total
may sometimes be effective. Often, a 40 percent
red/60 percent green/0 percent blue combination
is a good starting point.
4. Click on OK to make the conversion.
Figure 15-37. When the
Desaturate
command is used, the
image displays gray values, but remains in a color mode.
The left side of this image was desaturated, while the
original color was retained on the right side to permit
comparing the gray and color values.
Figure 15-38. The sponge tool can “wipe away” color in
selected areas for effect. Different opacity settings can
alter the effect, leaving a tint of color in place.
percent to remove all color, or set to a lower
value to leave a tint of the color in the area.
See Figure 15-38.
The
Channel Mixer
command provides the
greatest degree of control when converting a
color image to monochrome. It permits you to
select different percentages from each of the color
channels while observing (in monochrome) the
effects of the changes.
Figure 15-39. A scene can be given a different interpre-
tation by varying the channel percentages using the
Channel Mixer
command. A—Combining 40 percent
red channel, 60 percent green channel and 0 percent
blue channel provides a good tonal range. B—This
lighter interpretation combines 30 percent red channel,
80 percent green channel and 0 percent blue channel.
A B

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421
Making a Monochrome Conversion Using the Channel Mixer
1. Open the image you wish to convert.
2. Click on Image Adjustments Channel Mixer. Select the Monochrome check box at the lower-left corner
of the Channel Mixer dialog.
3. Try different combinations of the channel sliders
while observing the effect on the monochrome
image,
Figure 15-39.
The percentages usually
should add up to 100, although a higher total
may sometimes be effective. Often, a 40 percent
red/60 percent green/0 percent blue combination
is a good starting point.
4. Click on OK to make the conversion.
Figure 15-37. When the
Desaturate
command is used, the
image displays gray values, but remains in a color mode.
The left side of this image was desaturated, while the
original color was retained on the right side to permit
comparing the gray and color values.
Figure 15-38. The sponge tool can “wipe away” color in
selected areas for effect. Different opacity settings can
alter the effect, leaving a tint of color in place.
percent to remove all color, or set to a lower
value to leave a tint of the color in the area.
See Figure 15-38.
The
Channel Mixer
command provides the
greatest degree of control when converting a
color image to monochrome. It permits you to
select different percentages from each of the color
channels while observing (in monochrome) the
effects of the changes.
Figure 15-39. A scene can be given a different interpre-
tation by varying the channel percentages using the
Channel Mixer
command. A—Combining 40 percent
red channel, 60 percent green channel and 0 percent
blue channel provides a good tonal range. B—This
lighter interpretation combines 30 percent red channel,
80 percent green channel and 0 percent blue channel.
A B

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420
Section III Digital Postprocessing
Figure 15-36. Converting from color to grayscale. A—The original color image. B—A straight conversion using the
grayscale command can result in a flat image because of similar brightness values of different colors. C—Selecting
the best color channel and converting it to grayscale can provide better contrast.
A B C
Figure 15-35. You can use the
Color Replacement
tool
brush to paint a new color over an object while retaining
the original surface texture. The crosshair in the center
of the brush circle is placed on the color to be replaced.
A mouse click will then make the color replacement in
the area covered by the brush circle.
color to a shade of gray, similar brightness values
make it difficult to distinguish a red flower from
its background of green leaves. Further processing
of the converted image using
Levels
or
Curves
can
improve the contrast.
An alternate conversion method that often
gives better contrast is to review the color
channels (which are displayed in grayscale)
and select the one that looks best. With the
desired layer selected, the
Grayscale
command
will use the brightness values of that channel
to make the conversion. Figure 15-36 shows the
results of the two conversion methods.
When the
Desaturate
command is
used, Figure 15-37, color is removed from
the image, and gray values are displayed.
The image remains in the color mode, with
the three color channels still intact. This
situation increases the possibilities for image
manipulation, such as adding areas of color
or restoring some portions of the image to
their original color values (see Using the
History Brush, in Chapter 16).
To desaturate only part of an image so that
some areas are gray and others in color, two
different techniques may be used. A selection
may be made to isolate the desired part of the
image, and the
Desaturate
command applied
to the selected area. Direct desaturation can be
done with the
Sponge
tool. This tool, located
with the
Dodge
and
Burn
tools on the toolbox,
is applied like a paintbrush or eraser tool to
the desired area. Opacity can be set to 100

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420
Section III Digital Postprocessing
Figure 15-36. Converting from color to grayscale. A—The original color image. B—A straight conversion using the
grayscale command can result in a flat image because of similar brightness values of different colors. C—Selecting
the best color channel and converting it to grayscale can provide better contrast.
A B C
Figure 15-35. You can use the
Color Replacement
tool
brush to paint a new color over an object while retaining
the original surface texture. The crosshair in the center
of the brush circle is placed on the color to be replaced.
A mouse click will then make the color replacement in
the area covered by the brush circle.
color to a shade of gray, similar brightness values
make it difficult to distinguish a red flower from
its background of green leaves. Further processing
of the converted image using
Levels
or
Curves
can
improve the contrast.
An alternate conversion method that often
gives better contrast is to review the color
channels (which are displayed in grayscale)
and select the one that looks best. With the
desired layer selected, the
Grayscale
command
will use the brightness values of that channel
to make the conversion. Figure 15-36 shows the
results of the two conversion methods.
When the
Desaturate
command is
used, Figure 15-37, color is removed from
the image, and gray values are displayed.
The image remains in the color mode, with
the three color channels still intact. This
situation increases the possibilities for image
manipulation, such as adding areas of color
or restoring some portions of the image to
their original color values (see Using the
History Brush, in Chapter 16).
To desaturate only part of an image so that
some areas are gray and others in color, two
different techniques may be used. A selection
may be made to isolate the desired part of the
image, and the
Desaturate
command applied
to the selected area. Direct desaturation can be
done with the
Sponge
tool. This tool, located
with the
Dodge
and
Burn
tools on the toolbox,
is applied like a paintbrush or eraser tool to
the desired area. Opacity can be set to 100

Section III Digital Postprocessing
422
Cleaning up the Image
Despite the most careful cleaning of a
negative before printing in the conventional
darkroom, at least a few small white dust spots
are likely to turn up on the final print. These
must be eliminated by the use of dye solutions
and a very fine-pointed brush. The process,
called spotting, is tedious and takes some practice
to achieve acceptable results. The process is
described in Chapter 21, Advanced Printing.
The digital darkroom makes the spotting
task much easier, but careful cleaning of scanned
materials is still necessary to minimize the
problem. When scanning from prints, the glass
of the flatbed scanner should be inspected and
cleaned if necessary; negatives and slides should
be dusted with a soft (preferably antistatic) brush
before being inserted in the film scanner.
Spotting may also be necessary on images
captured with a digital SLR camera: when the
camera body is opened to change lenses, dust
and lint particles can enter and settle on the cover
plate of the sensor. The particles show up as dark
spots when the image is displayed. They are
especially noticeable in areas of light, continuous
tone such as the sky or an expanse of snow or
sand.
Spotting is done with the
Clone Stamp
tool,
which is used to copy (clone) a small area of the
image and place it over the dust spot. The size
of the copied area and the nature of the copied
information (hard- or soft-edged and the degree
of opacity) can be varied to suit the situation. The
working size of the
Clone Stamp
tool is set by
choosing a brush size from the
Brushes
palette;
for spotting work, a fairly small soft-edged brush
is normally used.
Figure 15-41 shows a portion of a scanned
antique image that requires spotting. Note
that only a portion of the image is visible—all
spotting work should be done with the image
at the full size (100 percent) setting. This allows
you to see what the image will look like when
printed, so that defects can be identified and
corrected. Spotting should be done systematically,
beginning at one of the image corners and
proceeding in steps until the entire image has
been processed. The
PAGE UP
and
PAGE DOWN
keys allow you to step through the image
vertically; combined with the
CTRL
key, they
allow horizontal stepping.
A major drawback to using the preceding
methods for monochrome conversion is that they
are destructive: once the image has been saved,
the change cannot be reversed. The best choice
is the use of a
Black & White
adjustment layer.
Adjustment layers are nondestructive, meaning
the images can be saved and closed, then opened
again, and the changes removed to bring the
image back to its original state.
Like
Channel
Mixer, the
Black & White
adjustment layer allows you to adjust color sliders
and try different combinations to find the best
monochrome conversion. Instead of the three
(red, green, and blue) color sliders in the
Channel
Mixer, however, the
Black & White
adjustment
layer has six: reds, yellows, greens, cyans, blues,
and magentas. See Figure 15-40.
An alternate adjustment method to the color
sliders is the
Target adjustment
tool. Place the
tool cursor on an area of tone you wish to alter.
Then, click the mouse button and drag the tool,
observing the changes on the image preview.
Once you are satisfied with the conversion, close
and save the image. If you later wish to try a
different set of adjustments, open the file and
click on the
Black & White
adjustment layer in
the
Layers
palette. You can then make additional
changes and resave the file.
Figure 15-40. A
Black & White
adjustment layer is easily
created by clicking its icon on the
Adjustments
panel.
The monochrome conversion can be altered by using the
color sliders, or by clicking on the
Target
adjustment tool
and placing it on an area to be altered.
Target
adjustment
tool

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Page 375Section III Digital Postprocessing click to expand contents

Page 487Section IV Traditional Processing click to expand contents

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