Sử dụng photoshop cs5 part 33 ppt

To delete an adjustment layer: Do either of the following: Click the icon for an adjustment layer on the Layers panel, then click the Delete Layer button on the same panel or the Delete

Merging and deleting adjustment

layers

When you merge an adjustment layer downward, the

adjustments are applied permanently to the

under-lying image layer If you change your mind, either

choose Edit > Undo (right away!) or click the prior

state on the History panel

To merge an adjustment layer:

Do either of the following:

Click the adjustment layer to be merged

downward,A then press Ctrl-E/Cmd-E.B

Right-click on or near the adjustment layer name

and choose Merge Down.

Note: Adjustment layers don’t contain pixels,

so you can’t merge them with one another

However, you can merge multiple adjustment

layers into an image layer (or layers) by using the

Merge Visible command (see page 145) or the

Flatten Image command (see page 146)

Adjustment layers are as easy to delete as they are

to create

To delete an adjustment layer:

Do either of the following:

Click the icon for an adjustment layer on the

Layers panel, then click the Delete Layer

button on the same panel or the Delete

Adjustment Layer button on the Adjustments

panel Click Yes if an alert appears Optional:

Click Don’t Show Again to prevent the alert from

reappearing

Click the icon or layer mask thumbnail for an

adjustment layer on the Layers panel, then press

Backspace/Delete (See also the sidebar at right.)

A Click the adjustment layer to be merged downward.

B The Merge Down command applied the Levels values from the adjustment layer to the underlying image layer, which in this case is the Background.

BYPASSING THE AUTO-SELECT PARAMETER OPTION ★

The new Auto-Select Parameter option (on the Adjustments panel menu) causes the fi rst entry fi eld

on the panel to become highlighted automatically when you create an adjustment layer or when you double-click the icon for an existing adjustment layer on the Layers panel Although this option enables you to quickly enter or change values, it can be an annoyance because it prevents some shortcuts from working (e.g., selecting a tool via its letter shortcut or deleting a layer by pressing Backspace/Delete) If this option is on and you want to shift the focus from the Adjustments panel

to the Layers panel, click either the icon or the layer mask thumbnail for the adjustment layer

202 Chapter 12

Editing the adjustment layer mask

By default, every adjustment layer has a blank white

layer mask To limit which area of the image the

adjustment affects, you can add black areas to the

mask, either by filling a selection or by applying

brush strokes, as we show you in the steps below

To edit the adjustment layer mask:

1 Click the mask thumbnail on an adjustment layer.

2 Press D to choose the default colors, then press

X to switch to black as the Foreground color

3. To partially mask the adjustment layer effect,

do either or both of the following:

Create a selection with any selection tool (e.g.,

Rectangular Marquee or Lasso), choose Edit >

Fill (Shift-Backspace/Shift-Delete), choose Use:

Foreground Color, click OK, then deselect.

Choose the Brush tool (B or Shift-B) On

the Options bar, choose a Soft Round brush,

Mode: Normal, and an Opacity of 100% (or a

lower opacity to create a partial mask), adjust

the brush diameter by pressing [ or ], then apply

brush strokes to the image.A–C

4 Optional: To reverse the effect of the mask in

specific areas, press X to switch colors (make the

Foreground color white), then with the Brush

tool, apply strokes to remove the mask

➤ To remove all black areas from the mask, deselect,

click the adjustment layer mask, choose Edit >

Fill, then choose Use: White in the dialog

➤ To confine the effect of an adjustment layer to

a small area, start with a fully black mask (click

Invert on the Masks panel or apply Edit > Fill,

Use: Black), then apply strokes with white

➤ To create a gradual mask by applying a gradient,

see pages 244–245 To refine the edge or density

of the mask, see pages 170–171

SHORTCUTS FOR LAYER MASKS

View the mask by itself in the docu-ment window

Alt/Option click the layer mask thumbnail (repeat to restore the normal view) View the mask

over the image as

a Quick Mask (the default color is red)

Alt-Shift/Option-Shift click the layer mask thumbnail (repeat to restore the normal view)

Deactivate or activate the mask

Shift-click the layer mask thumbnail (Layers panel)

or click the Disable/Enable button (Masks panel) Convert the

unmasked area into

a selection

Ctrl/Cmd click the layer mask thumbnail (Layers panel) or click the Load Selection from Mask button (Masks panel)

BWe used Curves to correct the color, then with the mask for that adjustment layer selected, we applied brush strokes to the top part of the image Now the adjustment is visible in only the bottom half of the photo.

AThis original photo looks too pink.

COur brush strokes are rep-resented by black areas in the adjustment layer mask thumbnail.

Using the Histogram panel

The Histogram panel displays a graph of the

current tonal (light and dark) values in an image,

which updates dynamically as the document is

edited The panel is always accessible, even while the

Adjustments panel is being used or an adjustment

dialog is open You can better judge how adjustment

edits are affecting your document if you monitor the

changes in its histogram

After opening a photo into Photoshop — but

before you begin editing it — study the histogram to

evaluate the existing distribution of tonal values in

the image The horizontal axis on the graph

repre-sents the grayscale or color levels between 0 and 255,

the vertical bars represent the number of pixels at

specific color or tonal levels, and the contour of the

graph represents the overall tonal range

To choose a view for the Histogram panel:

From the Histogram panel menu, choose one

of the following: Compact View (just the

histogram),A Expanded View (the histogram

plus data and access to individual channels),B or

All Channels View (all the features of Expanded

View, plus separate histograms for each channel)

To display document data in the latter two views,

check Show Statistics

For Expanded or All Channels view, choose an

option from the Channel menu: RGB, C a specific

channel, Luminosity, or Colors To display

the individual channels in color, check Show

Channels in Color on the panel menu

While a large file is being edited, Photoshop

main-tains the redraw speed of the Histogram panel by

reading the data from the histogram cache — not

from the actual image When this is occurring, a

Cached Data Warning icon appears on the panel

Remember to keep updating the panel, as we instruct

you here (even while editing the settings for an

adjustment layer), so it will continue to reflect the

current tonal values of the image

To update the Histogram panel:

Do one of the following:

Double-click anywhere on the histogram

Click the Cached Data Warning icon.

Click the Uncached Refresh button

➤ To specify a Cache Levels value in the Preferences

dialog, see page 391

C With RGB chosen on the Channel menu, the current tonal values in the image are represented by black areas

on the graph.

B Here the panel is in Expanded View By default, the Channel menu is set to Colors.

A This Histogram panel is in Compact View.

204 Chapter 12

Interpreting the Histogram panel

To focus on tonal values when using the Histogram

panel, choose Expanded View from the panel menu

and choose RGB from the Channel menu Pixels are

represented by vertical bars in the graph, with

shad-ows on the left, midtones in the middle, and

high-lights on the right For a dark, low-key image (such

as a night scene), the bars will be clustered primarily

on the left side of the graph; for an average-key image

with more balanced lights and darks, the bars will

be more uniformly distributed across the graph; and

for a very light, high-key image containing few or no

shadow areas, the bars will be clustered primarily on

the right side

If an image has a wide tonal range, the bars will

be more uniformly distributed in all the tonal zones,

and will stretch fully from one end of the graph to

the other Also, the graph will be mostly solid and will

have a relatively smooth contour rather than a spiky

one.A If an image lacks detail in a particular tonal

range, on the other hand, the graph will contain gaps

and spikes, like teeth on a comb The following are

some graph profiles that you might encounter:

➤ For an average-key but underexposed image that

lacks details in the highlights, pixels will be

clus-tered primarily on the left side of the histogram.B

➤ For an overexposed image that lacks details in the

shadows, pixels will be clustered mostly on the

right side of the histogram.C

➤ For an image in which pixels were clipped (details

discarded) from the extreme shadow or highlight

areas, a line or cluster of pixels will rise sharply

at the left or right edge, respectively, of the

histogram.D

➤ If an image has lost details as a result of editing

(such as from filters or adjustments), the

histo-gram will have gaps and spikes.E The gaps indicate

a loss of specific tonal or color levels, whereas the

spikes indicate that pixels from different levels

have been averaged together and assigned the

same value (the bar becomes taller at that level)

A few gaps and spikes are an acceptable result of

editing, whereas large gaps signify that

posteriza-tion has occurred and too many continuous tonal

values have been discarded On the other hand,

a lousy-looking histogram doesn’t always signify

failure — the graph can be thrown off by

some-thing as simple as adding a white border If you

like the way the image looks, ignore the histogram!

A The tonal ranges in this image are well balanced.

B The histogram shows this image is underexposed

C This image is overexposed.

D This graph shows that shadow pixels are clipped.

E This graph contains gaps and spikes.

IN THIS CHAPTER

Correcting tonal values using a Levels adjustment layer 206 Applying a Brightness/Contrast adjustment 208 Applying a Photo Filter adjustment 209

A quick and dirty method for correcting under- or overexposure 210 Dodging and burning small areas 211 Converting layers to grayscale via

a Black & White adjustment 212 Applying a Vibrance adjustment 214 Applying a Color Balance adjustment 217 Applying a Hue/Saturation

adjustment 219 Applying an Auto Color Correction 220 Correcting the color using Curves 222 Applying the Shadows/Highlights command 227 Applying a tint via a Solid Color

fi ll layer 231 Screening back a layer using Levels 232

13

Photoshop, take a few minutes to

study it and see if it has any tonal

or color defects Is it over- or

under-exposed? Does it have a color cast

(does it look ghostly blue or sickly

green)? To some extent, the subject matter of the

photo will dictate what kind of adjustments it needs

For instance, we might rebalance the skin tones in

a portrait to make it look more natural, but apply a

tint or photo filter to a photo of an abstract texture

or to an extreme closeup for an artistic effect

If you capture your photo as raw files or in the

JPEG or TIFF format, you will be able to rectify

many of their defects in Camera Raw If you can’t

use Camera Raw for your files or they need further

correction, not to worry: Photoshop offers a

smor-gasbord of adjustment controls Each adjustment

type has a specialized function (see the icons below)

Some are easy to get the hang of, and others may

take longer to master but offer more power or more

nuanced controls

In the preceding chapter, we stepped you through

the mechanics of creating and working with

adjust-ment layers In this chapter, we delve into their

specific features The good news is that by the end of

this chapter, you will have mastered most of the key

Photoshop commands!

BUTTONS ON THE ADJUSTMENT PANEL

Invert

Posterize Gradient Map

Selective Color Threshold

Vibrance

Hue/

Saturation Black & White

Channel Mixer

Photo Filter Color

Balance

Brightness/

Contrast Levels Curves Exposure

Continued on the following page