Chapter 10

Enhancing Specific Selections

Chapter Lessons

• Create an alpha channel• Isolate an object• Erase areas in an image to enhance appearance• Use the Clone Stamp tool to make repairs• Use the Magic Wand tool to select objects• Learn how to create snapshots• Create multiple-image layouts

Using Channels

• Nearly every image opened or created in Photoshop is separated into channels

• Channels are used to house the color information for each layer and layer mask in an image

Fixing Imperfections

• Isolate areas• Erase areas using a variety of eraser tools• Take a sample and then paint that sample over

an area using the Clone Stamp tool

Creating Snapshots

• Use the snapshot command to make a temporary copy of any state of an image

• The snapshot is added (above the states) at the top of the History panel

Advantages of Snapshots

• Name a snapshot to make it easy to identify and manage

• Compare changes to images easily: take a snapshot before and after making changes

• Recover work easily

Using Automation Features

• Create an image that contains various sizes of the same image or several different images

• Print images in a variety of sizes and shapes on a single sheet

• Create a contact sheet consisting of thumbnail images

Create an Alpha Channel

• Created automatically in a new image• Used to store color information about images• Example:

– A CMYK image has at least four channels (cyan, magenta, yellow, black)

More on Channels

• An image can consist of from 1 to 24 color channels

• Default channels are color channels contained in an image and created automatically

• Add Alpha or Spot channels to images displayed in all color modes, except the bitmap modes

Alpha and Spot Channels

• Alpha Channels and Spot Channel specify color information added to the image

• Alpha channel is used to:– Create and store masks to manipulate, isolate,

or protect parts of an image• Spot channel contains:

– Information about special pre-mixed inks used in CYMK color printing

Understanding Alpha Channels

• Create on the Channels panel• Can create an alpha channel that masks all or

specific areas of a layer• Use alpha channels to:

– Preserve a selection for experimentation– Use later– Create special effects – Save and reuse in other images

Saving an Alpha Channel

• Use the following formats to save an alpha channel:– PSD– PDF– PICT– TIFF– Raw

Alpha channels do not print

Understanding the Channels panel

• Lists all the default channels contained in a layer• Manages all the image’s channels• To access:

– Click the Channels tab next to the Layers tab

Order of Channels

• On the Channels panel, channels appear in the following order:– Composite channel: combination of other default

channels– Additional default channels that are based on

existing color modes– Spot color channels– Alpha channels

Channels Panel

Channel Properties

• Hide channels• Re-order channels• View channels as thumbnails on the Channels

panel

Creating an Alpha Channel

• Select a portion of an image• Click the Save selection as channel button on the

Channels panel• Double-click the Alpha 1 thumbnail on the

Channels panel• Click the color box in the Channel Options dialog

box• Set the color and select options

Alpha Layer ExampleBefore

Red alpha channel overlaying purple produced violet

After

Isolate an Object

• Use the Extract plug-in to isolate a foreground object from its background

• After extracting an image, modify the extracted object layer as required

Using Extract

• Use tools in the Extract dialog box to extract objects:– Use the Edge Highlighter tool to trace the edge

of the object to extract– Use the Fill tool to select everything inside the

edge

Extract Plug-in Tools

Enhance Appearance with Eraser Tools

• Use eraser tools to erase an area without going through the extraction process

• Three eraser tools are available:– Eraser tool– Background Eraser tool– Magic Eraser tool

Eraser Tool Examples

Magic Eraser erases similarly colored pixels

Background Eraser exposes transparency

of the layer below

Eraser tool exposes

background color

Fix Imperfections in an Image

• Use the Clone Stamp tool to copy a sample in an image, then paste it over an area to cover

• Size of the sample taken depends on the brush tip size selected

Using the Clone Stamp Tool

Object to delete

Sampled area applied to hide portions of the

object

Use the Magic Wand Tool to Select Objects

• Use the Magic Wand tool to choose pixels that are similar to pixels clicked in an image

• Specific tolerance settings• Specify whether to select only contiguous pixels

Understanding Tolerance

• Tolerance setting determines the range of colors that can be selected with the Magic Wand tool

• Example:– Low tolerance: Magic Wand tool selects a

narrow range of pixels– High tolerance: Magic Wand tool selects a wider

range of pixels

Using the Eyedropper Tool

• Area selected by the Magic Wand tool is related to the settings for the Eyedropper tool

• While working with the Magic Wand tool, verify or change Eyedropper tool settings as needed

Learn How to Create Snapshots

• Create a snapshot of the image at various stages:– Before beginning an editing session– After crucial changes have been made

• Use the snapshot to revert to original image settings, if required

Creating a Snapshot

• Click the Create new snapshot button on the History panel

• Each new snapshot is numbered consecutively, and can be renamed

• Snapshots appear in order at the top of the History panel

Snapshot Commands: History panel

Create Multiple-Image LayoutsUnderstanding a Picture Package

• Created in Adobe Bridge• Generate multiple-image layouts• A picture package can contain multiple sizes of a

single image• Can be saved as a PDF

Sample Picture Package

Assembling a Contact Sheet

• Assemble a maximum of 30 thumbnail images per page within a folder