Sử dụng photoshop cs5 part 34 pot

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206 Chapter 13
When performing adjustments, please consider
these suggestions:
➤ Make sure your monitor is properly calibrated
rst (see pages 7–9). Also learn how to create
a soft proof of your document so you can get
an inkling of how it will look when printed (see
pages 404–405.
➤ Digital photos are captured in RGB Color mode
automatically. Keep them in this mode for
adjustments. Should you need to adjust an image
for a specic CMYK output device, do so on a
copy of the le, not on the original. (e docu-
ment color mode of high-resolution CMYK scans
shouldn’t be changed, either.)
➤ Put your document into Standard Screen mode
(choose that option from the Screen Mode
menu on the Application bar); Mac OS users
should also display the Application frame. e
gray area around the image will provide a good
neutral backdrop for judging your color and tonal
corrections.
Correcting tonal values using a
Levels adjustment layer

Now that you know how a read a histogram (see
pages 203–204), you’re ready to create a Levels
adjustment layer. Levels has a histogram of its own.
We usually use Levels when we rst bring a photo
into Photoshop, then sometimes use it again during
the course of editing. In the following steps, you will
use Levels to correct tonal values (Levels is also used
on pages 220–221 and page 232).
To correct tonal values using Levels:
1. Click a layer that needs a contrast adjustment,
A
then on the Adjustments panel, click the
Levels button. e Levels controls display.
2.
Do any of the following:
B
To intensify the contrast, brighten the highlights
by moving the white Input Levels high lights
slider to the left and darken the shadows by
moving the black Input Levels shadows slider
to the right. Any pixels located to the left of the
black slider will become black; any pixels located
to the right of the white slider will become white.
(is shifting of tonal values is called “clipping.”)
Another way to gure out where to position
the highlights and shadows sliders is to activate
 r e s h o l d m o d e , a t e m p o r a r y , h i g h - c o n t r a s t

A
 e o r i g i n a l i m a g e l a c k s c o n t r a s t ( l o o k s d u l l ) .

B
 e h i s t o g r a m i n t h i s L e v e l s p a n e l d o e s n ’ t e x t e n d a l l
the way to the edges, an indication that the tonal range
of this photo is narrow. To expand the range, we moved
the shadows and highlights Input Levels sliders inward to
align with the outer edges of the histogram, and moved
the midtones slider to the right to darken the midtones.
Midtones HighlightsShadows
Output Shadows Output Highlights
Input
Levels
sliders
Output
Levels
sliders

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Adjustments in Depth 207
display of clipping. Alt-drag/Option-drag the
highlights slider, and release the mouse when
only a few areas of color or white display;
A
these
pixels will become the lightest tonal value. Also
Alt-drag/Option-drag the shadows slider, releas-
ing the mouse when only a few areas of color

or black appear;
B
these pixels will become the
darkest tonal value.
3. With the shadows and highlights sliders now
in their proper positions, move the gray Input
Levels midtones slider to lighten or darken
the midtones separately from the shadows or
highlights.
C–D
➤ To apply the current Levels settings to other
open images (perhaps images that were taken
under similar lighting conditions, that require
the same adjustments), choose Save Levels Preset
from the Adjustments panel menu. Enter a name
for the preset (keep the default location), then
click Save. Click another document tab, and click
an image layer in that document. Expand the
Levels Presets list on the Adjustments panel,
then click your new preset at the bottom of the
list. A Levels adjustment layer will be created,
using your saved settings.

B
 i s i s  r e s h o l d
mode as we Alt-drag/
Option-drag the
black Input Levels
(shadows) slider.

D
 e L e v e l s a d j u s t m e n t s e x p a n d e d t h e t o n a l
range of the image; now the bars extend from one
end of the graph to the other.

C
Our Levels adjustments improved the contrast (the
shadows and highlights are intensied).

A
 i s i s  r e s h o l d
mode as we Alt-drag/
Option-drag the
white Input Levels
(highlights) slider.

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208 Chapter 13
To subtly tweak the brightness or contrast in an
image, try using the simple but powerful Brightness/
Contrast controls.
To apply a Brightness/Contrast adjustment:
1. Click a layer or the Background.
2.
On the Adjustments panel, click the
Brightness/Contrast button. e Brightness/
Contrast controls display.
3.
Move the Brightness and/or Contrast

sliders.
A–D

➤ Keep the Use Legacy option for Brightness/
Contrast unchecked, as it would permit tonal
levels to be eliminated from the image. With this
option o, pixel data from the entire tonal range
is preserved; after adjustment, you’ll see evidence
in the histogram of only a minor redistribution
in tonal values.

A
 e o r i g i n a l i m a g e l o o k s a b i t d u l l ( i t l a c k s c o n t r a s t a n d
the color is undersaturated).
B
Using the Brightness/Contrast settings shown above,
we increased the brightness of the overall image and
increased the contrast to make the colors more saturated.

C
 e s k i n t o n e s i n t h e o r i g i n a l i m a g e
look washed out.
D
Using the settings shown at left, we
decreased the brightness of the overall
image and then increased the contrast
to boost the saturation of the skin tones.
Applying a Brightness/Contrast adjustment

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Adjustments in Depth 209
Applying a Photo Filter adjustment





To change the color temperature of a scene (make
it look warmer or cooler), photographers use
colored lens lters at the time of the shoot. In
Photoshop, you can simulate the eect of a camera
lter by using a Photo Filter adjustment layer,
to neutralize a color cast or to apply a tint (as a
special eect). You can choose from 20 preset tints
or choose a custom color. When using this feature,
go for subtle or extreme, but not in between.
To apply a Photo Filter adjustment:
1. Click a layer or the Background.
A
2. On the Adjustments panel, click the Photo
Filter button. e Photo Filter controls
display.
B






3. Do either of the following:

Click Filter, then from the menu, choose a
preset warming or cooling lter or a lter color.
e lter color displays in the swatch.
Click the Color swatch, choose a color for the
lter from the Color Picker (note the change in
the image), then click OK.
➤ For a subtle change, pick a related color; for
a more obvious change, pick a complemen-
tary color (opposite on the color wheel).
4.
Using the Density slider or scrubby slider,
choose an opacity percentage for the tint. Try
a modest value between 10% and 25%, or a
higher value for a dramatic change.
C
You can
also lower the opacity of the adjustment layer.
5.
Check Preserve Luminosity to preserve the
overall brightness and contrast of the image.
With this option unchecked, the contrast will
be softer in the highlights, but the resulting
colorization eect may be too pronounced. For
a portrait, you may prefer the results with this
option o.
6.
To compare the original and adjusted images,
click the Layer Visibility button on the
Adjustments panel o and then on again (or
do likewise with the visibility button for the

adjustment layer on the Layers panel).

A
 e o r i g i n a l
image has a
magenta cast.
B
For our Photo
Filter adjustment
layer, we chose
Cyan from the Filter
menu and left the
Density at 25%.

C
 e P h o t o F i l t e r a d j u s t m e n t r e m o v e d t h e
magenta cast but preserved the warm tones
from the afternoon sun.

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210 Chapter 13
A quick and dirty method for
correcting over- or underexposure


For a quick and dirty way to correct an over- or
underexposed photo, create an adjustment layer,
choose a blending mode for the layer that has a light-
ening or darkening eect, then duplicate it a few
times. It’s not the most precise method in the world,

but if it works, it works (and if it makes your art
director happy, maybe you can go home early!).
To correct the exposure via the Layers panel:
1. Open an over- or underexposed photo,
A
and
click the Background or a layer.
2.
On the Adjustments panel, click the Levels
button. Leave the settings as they are.
3.
On the Layers panel, click the new adjust-
ment layer, then choose a blending mode that
produces a lightening or darkening eect. For
example, to darken an overexposed image, you
could try Multiply mode, or to lighten an under-
exposed image, try Screen or Lighten mode.
4.
If the image is still too light or dark, duplicate
the adjustment layer by pressing Ctrl-J/Cmd-J.
B
Repeat the shortcut until you reach a point
where the image is slightly overcorrected and you
need to step it back a bit.
5.
Lower the opacity of the topmost adjustment
layer until the exposure looks just right.
C

A

 e o r i g i n a l i m a g e i s u n d e r e x p o s e d .
B
We created an adjustment layer, chose Screen
blending mode, duplicated the layer, then lowered
the opacity of the duplicate adjustment layer to 47%.

C
 e t w o L e v e l s a d j u s t m e n t l a y e r s p r o d u c e d t h i s r e s u l t .

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Adjustments in Depth 211
Dodging and burning small areas


To lighten or darken pixels by hand in small areas,
you might instinctively reach for the Dodge and
Burn tools. However, those tools, even with their
new enhancements, permanently alter layer pixels.
A better method is to dodge and burn areas with the
Brush tool on a removable, editable neutral color
layer, as in the steps below.
To dodge and burn areas via a neutral
color layer:
1. If the document isn’t in RGB Color mode, convert
it by choosing Image > Mode > RGB Color.
2. Click an image layer or the Background,
A
then
Alt-click/Option-click the New Layer button.
e New Layer dialog opens.

3. Choose Mode: Overlay, check Fill with Overlay-
Neutral Color (50% gray), then click OK.
4. Choose the Brush tool (B or Shift-B). From
the Options bar, choose a Soft Round brush and
an Opacity of 20%. Press [ or ] to set the brush
diameter.
5. Press D to make the Foreground color black,
then apply brush strokes to areas that you want
to darken. To lighten areas, press X to swap the
Foreground and Background colors (make the
Foreground color white), then apply strokes.
B–C
6. Optional: To remove any unwanted dodge or burn
strokes, hide the image layer. Alt-click/Option-
click to sample the gray value in an untouched
area, then with a brush opacity of 100%, paint
over those strokes. Redisplay the image layer.
➤ To lessen the whole dodge or burn eect, click
the neutral gray layer on the Layers panel, then
lower the layer opacity or choose Soft Light as
the layer blending mode.
B
When displayed by
itself, a neutral gray
layer looks like this.

…then applied white
strokes to lighten the
cobblestones around
the gure.

We applied black
strokes to darken the
shadows on the sides
of the buildings,…

C
We applied strokes to the neutral gray layer to
dodge the road and burn the houses, then lowered
the layer opacity to 78% to soften the eect.


A
 e c e n t r a l  g u r e i n t h i s i m a g e , w h e r e t h e f o c a l
point should be, lacks contrast. We’ll adjust the
reected light on the cobblestones to draw more
attention to that area.