Adobe Photoshop CS5 – Illustrated Unit B: Selecting Pixels

Adobe Photoshop CS5 – Illustrated

Unit B: Selecting Pixels

Objectives

Use the Marquee toolsUse the Lasso toolsUse the Magic Wand toolSave and load selections

Adobe Photoshop CS5 - Illustrated

Objectives

Work with and save alpha channelsUnderstand anti-aliased edgesWork with a feathered edgeRefine selection edges


Using the Marquee Tools

In order to modify pixels they first need to be selectedThe Marquee tools are the most basic tools available for making selections in Photoshop The Rectangular Marquee tool is used for making

rectangular or square selections The Elliptical Marquee tool is used for making oval

or circular selectionsPixels can be added to an existing selection and can be removed from a selection by using quick keys



The black triangle on some tool icons indicates that there are additional hidden tools beneath the currently displayed toolIf not happy with a selection then it can be deselected and started over




Positioning the first piece

Repositioning the circle piece

CLASSROOM ACTIVITIES

True/False. The Elliptical Marquee tool is used for

making oval or circular selections. (Answer: True)

What does the shift key do? (Answer: it adds to an existing

selection, and it constrains a selection to a perfect shape)


Using the Lasso Tools

There are three types of Lasso tools in Photoshop Lasso, Polygonal, and Magnetic

Lasso tools are used for making free-form selections click and drag anywhere on the canvas to create a

section of pixels• it is usually easier to make small selections and

use the Shift key to add them to create a more complex shape

the Polygonal Lasso tool functions like the Lasso Tool but with straight lines making it great for selecting shapes that are geometric


Using the Lasso Tools


Selecting the interior of the object

Positioning the fifth piece


What are the three types of Lasso tools?

(Answer: Lasso, Polygonal, and Magnetic)Which key do you press to add small selections of pixels?

(Answer: Shift)


Using the Magic Wand Tool

The Magic Wand tool is very powerfulClick any pixel on the canvas and the Magic Wand tool selects other pixels based on tolerance-the similarity of their colors the greater the tolerance value that is set for

the tool, the more pixels it will select click the Contiguous check box on the Options

bar to specify that the Magic Wand tool selects only pixels that are contiguous (touch) the area• otherwise the Magic Wand tool will select

similar pixels throughout the image



As with any selection, once the pixels are selected that are needed they can be modified in many waysZooming in on areas of the image that are to be selected always helps when making selections including colors using the Hue/Saturation dialog box




Selecting the white pixels

Selecting pixels without the Contiguous option

Results of changing the hue of selected pixels

CLASSROOM Activities

Discuss the difference between tolerance and contiguous. What is the first step you should do before modifying the object?

(Answer: Select it)


Saving and Loading Selections

Making selections can be some of the most complex and time-consuming work when using PhotoshopIt makes sense then to be able to save selections with the Photoshop fileSaving a selection is always a smart idea so that it can be easily accessed in the future


Saving and Loading SelectionsSaving Color Swatches

The Swatches panel can be used to change the foreground and background colors click a swatch and the foreground color changes click the Eyedropper tool and sample any pixel

from the image which also changes the foreground color

To save colors that are created, simply float the pointer over a white area of the Swatches panel; when the pointer changes to a paint bucket icon click to add the color as a new swatch


Saving and Loading Selections


The finished project

Pure Yellow Orange swatch on the Swatches panel

Save Selection dialog box


What does posterize mean in Photoshop?

(Answer: Posterize is a special effect that is created by reducing the number of colors available for the image)True/False.

You can create and save selections and fill them with different colors.

(Answer: True)Adobe Photoshop CS5 - Illustrated

Working with and Saving Alpha Channel

Alpha channels are simply saved selectionsAlpha channels are listed on the Channels panel in Photoshop and are displayed as black and white thumbnail images the selected areas are represented by white and

the areas not selected by black

Alpha channels are not automatically saved when the file is saved; they need to be specified when saving a file


Working with and Saving Alpha Channel


The Dark Gray alpha channel

Save Alpha Channels option in the Save As dialog box


Where can you find the Alpha channels?

(Answer: They are listed in the Channels panel in Photoshop) What should you do if you begin working and the wrong foreground or background is selected. How would you make the corrections?


Understanding Anti-Aliased Edges

The outline of a selection is called the edgeThe type of edge selected has a big impact on the work appears the edge of a selection is always either aliased

(hard edge which are very blunt and obvious) or anti-aliased is a crisp but smooth edge

An anti-aliased edge in Photoshop creates a smooth transition between the edge and the background using many shades of edge pixel colors


Understanding Anti-Aliased Edges

Pixels are squares and a soft edge can not be made with squares; but the illusion can be created using anti-aliasing


Viewing the anti-aliased edge

Viewing the aliased edge


True/False.A square has a soft edge. (Answer:

False)How much resolution do most monitors have?

(Answer: 72 pixels per inch)


Working with a Feathered Edge

A feathered edge is a blended edgePhotoshop offers settings for controlling the length of the blend at the edgeThe feather value is equal to the length of the feathered edge when the feathered edge is applied to a selection,

the edge is equally distributed inside and outside the selection edge

A vignette is a visual effect created with a feathered edge the edge of the image, usually oval, gradually

fades away


Working with a Feathered Edge


Drawing the feathered oval selection

The selected pixels relocated


What is a feathered edge? (Answer: blended edge)

What is a vignette? (Answer: a visual effect in which an

image gradually fades away)


Refining Selection Edges

The Refine Edge dialog box offers a number of useful options for viewing and refining the edge of a selectionTwo key options in the dialog box are: the Feather slider, used to dynamically feather

a selection while previewing the result the Contract/Expand slider, used to reduce of

enlarge a selection• especially useful for removing halos from the

edge of a selection


Useful keyboard commands for the Refine Edge dialog box (Win & Mac)

Refining Selection Edges


The Refine Edge dialog box

Selection

The silhouette of the eagle against black


What are the two key options in the dialog box?

(Answer: the Feather slider and the Contract/Expand slider)2. What key allows you to toggle the Preview option on and off?

(Answer: [P])


Summary

The Marquee and Lasso tools provide different ways to select image pixelsThe Magic Wand tool selects other pixels based on tolerance-the similarity of their colorsSaving selections makes it easy to access the selection in the futureAfter sampling a color of a selection, the color can be saved in the Swatches panel


Summary

Alpha channels are saved selections that need to be specified as an alpha channel to be saved when saving an image fileImages edges are made up of pixels that are square a blunt square edge is an aliased edge an anti-aliased edge is one that is made to look

like a smooth edge

Edges can be feathered and refined


Documents

Adobe Photoshop CS5 – Illustrated Unit B: Selecting Pixels