Introduction to digital

imaging using Photoshop

Practical workbook

Aims and Learning Objectives

The aim of this document is to introduce the basics of image processing using Adobe
Photoshop.
By the end of this course you will be able to:
• crop an image;
• correct perspective problems;
• adjust the tone and colours of an image;
• sharpen an image;
• scale an image;
• retouch a damaged photograph;
• save an image in a suitable format;
• make selections using a variety of tools;
• blend images to create a seamless montage;
• add and edit text.

University of Bristol Information Services document photoshop-t1

Introduction to digital imaging using Photoshop (photoshop-t1)

Document Information

Course documents and files

If you are working in the training room the files you need are in C:\User\Graphics\
If you want to work through the practical tasks shown in this document on your own system, obtain
the necessary files from:
http://www.bristol.ac.uk/is/info/websupport/resources/photoshop-t1.html

Related documentation
None.

Introduction to digital imaging using Photoshop (Mar 06)

www.bristol.ac.uk/is/learning/documentation/photoshop-t1/photoshop-t1.doc
If you have any comments or queries about this document mail iser-docs@bristol.ac.uk.
This document may be used wholly or in part by the academic community, providing suitable
acknowledgment is made. It may not be used for any commercial or profit-making purpose without
permission. © 2006 University of Bristol. All rights reserved.
Introduction to digital imaging using Photoshop (photoshop-t1)

Contents
Document Information
Introduction to Photoshop.......................................................................................1
Colour management .................................................................................................6
Task 1 Getting started ........................................................................................10
Task 2 Cropping and correcting perspective problems..................................13
Task 3 Adjusting overall tone and colour ........................................................16
Task 4 Sharpening an image .............................................................................21
Task 5 Resampling an image.............................................................................24
Task 6 Optimising an image to a suitable format ............................................28
Task 7 Retouching a damaged photograph .....................................................31
Task 8 Working with selections ........................................................................34
Task 9 Blending images.....................................................................................39
Task 10 Working with text layers ........................................................................43
Appendix A Resolution and image size for printing ........................................ 46
Appendix B Further resources ........................................................................... 47
Introduction to digital imaging using Photoshop (photoshop-t1)

Introduction
There is little doubt that the use of digital images in learning, teaching and research projects
is growing. Typical uses include: supporting lectures and other presentations; creating Web-
based instruction and creating digital image archives. Another advantage of digital images is
that they can be delivered on a variety of supports: PowerPoint, Web, image database, CD-
ROM and print. It is therefore important to be familiar with image digitisation processes in
order to obtain images that are ‘fit for purpose’.
This document shows you how to apply image enhancement techniques using Adobe
Photoshop CS2.

Prerequisites
This document assumes that you are familiar with the use of a computer keyboard and
mouse, Microsoft Windows-based products and the use of a Web browser such as Netscape
or Internet Explorer.
Introduction to digital imaging using Photoshop (photoshop-t1)

Introduction to Photoshop
Photoshop is the ultimate Swiss army knife for all your imaging needs, from basic to highly
sophisticated image editing. For example you can simply enhance a photograph (remove red eye
effect and scratches, crop, etc.), or create a complex photo collage or a sophisticated Web
interface. Palette well
Palettes
Menu bar

Option bar

Toolbox

Active image area

Status bar Context menu

The main components of the Photoshop work area are:

• Menu bar - contains menus organised by tasks. For example, the Layers menu contains
commands for working with layers.
• Toolbox - contains tools for creating and editing images.
• Options bar – provides options for the currently active tool.
• Active image area (also called Document window) – displays the active open file. Several
images can be open at the same time, but only one can be active at a time.
• Palettes – help you monitor and modify images. They can be nested by dragging the title tab
of one into the body of another. Use the Window menu to show/hide palettes
Other useful elements are:
• Palette well – helps you organize the palettes in your work area.
• Status bar – located at the bottom of every document window, it displays useful information
about the image and brief instructions for using the active tool.
• Context menu – display commands relevant to the active tool, selection, or palette. You
access them by right-clicking on an image or palette item.
The Toolbox, Palettes and Active image area can easily be moved around the workspace by
clicking the top bar and dragging them.

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Introduction to digital imaging using Photoshop (photoshop-t1)

The Toolbox
Move Tool
Magic Wand Tool

Crop Tool

Hand Tool Zoom Tool

Set foreground/
background
color

The Photoshop CS2 Toolbox contains all the tools you need for manipulating and creating
images, for example, making selections, cropping, drawing, painting, erasing, moving,
magnifying, etc.
Some of the buttons represent families of tools rather than single tools. For example, the
Rectangular Marquee Tool is the default for selecting geometrical shapes, but if you right-
click on it, a palette pops out with more choices such as an Elliptical Marquee Tool.
Further options are available when you hold down the <Shift>, <Ctrl> or <Alt> keys as you
use a tool. For example, hold down <Shift> to select a circular shape with the Elliptical
Marquee Tool.

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Introduction to digital imaging using Photoshop (photoshop-t1)

Palettes
Palettes are one of the main means of accessing many of the features of Photoshop. You can
show and hide them using the Window menu. Alternatively, you can press the <Tab> key while
holding down <Shift> to hide/show them all.
Palettes can be moved around or nested (stacked behind one another) by dragging the title tab of
one palette onto the body of another.

To bring a palette to the front, just click its title tab.

You can also expand/collapse them by double-clicking on the title tabs.
If you don’t like having palettes floating
around, you may prefer accessing them from
the Palette well. To add a palette to the
Palette well, simply drag it into it as
illustrated on the right.
Clicking on the right pointing arrow in the
top right corner will bring out a menu specific
to the active palette.

Two of the most useful palettes are the Layers palette and the History palette:

The Layers palette

Layers are an essential part of Photoshop and you need to think of them as the building blocks to
every image that you create. Individual palettes and the toolbar can be displayed or hidden using
the Window menu (those with a tick mark next to them are visible).
The Layers palette enables you to control elements of an image by assigning separate layers to
each individual element. Layers allow you to work on one element of an image without disturbing
the others.

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Blending modes Layers palette menu

Hide/Show layer

Reveals layer effects

Layer name

Layer thumbnail

Delete layer

Link layers Add a layer style

Create a new layer
Add layer mask
Create a new group
Create new fill or
adjustment layer

The idea is that you stack layers (in the same way that you would stack sheets of acetate
transparencies) containing the various elements that will form your final image. There are different
types of layers:
• Image layers are transparent and may contain images or part of images. They can also be
used for drawing, filling with colour, etc. They contain pixel information only.
• Adjustment and fill layers allow you to make colour and tonal adjustments to your image
without permanently changing its pixel values.
• Type layers allow you to insert text in your image. A new Type layer is automatically added
above the active layer when using the Type Tool.
• Shape layers are filled with solid colours and the outline is defined with a vector mask
and/or a layer mask. A new Shape layer is automatically added above the active layer when
using one of the shape tools (Rectangle/Rounded Rectangle/Line/etc Tool).
In addition, you can manipulate each layer individually by applying various styles and effects
(blending, drop shadow, etc.), filters and masks.

The History palette

Every change that you make to your image is recorded in the History palette as a history state.

History palette menu

Create new document

from current state
History state

Create new snapshot

History state slider

Delete current state

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Introduction to digital imaging using Photoshop (photoshop-t1)

Just click on a state in the History palette to go back to that state (alternatively drag the History
state slider up or down to point to the state you wish to move to). The states below the one you
click on are dimmed and will be discarded if you continue to work from the selected state.
You can also delete states by dragging them into the wastebasket icon in the bottom right corner of
the palette (alternatively right-click on the name of the state you want to delete, then choose
Delete from the pop-up menu). Notice that this action will also delete all the subsequent states.
By default, the History palette will remember 20 states. You can change this by going to
Edit/Preferences/General.

Getting help
Photoshop has a comprehensive help tool (see illustration below). To open it, go to
Help/Photoshop Help.
A-Z Index

Adobe Photoshop Help Center

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Colour management
Colour settings
One problem with imaging software is the issue of screen, scanner and printer inconsistency. For
example, monitor brightness, contrast and resolution all affect the way an image is displayed.
Photoshop includes features to help ensure that screen colours will, as far as possible, resemble
the final image.
As a rule of thumb, the image mode should be set to RGB Color when working for screen display
and CMYK Color for printing. To check this, from the main menu, select Image/Mode.

The reason for this is the differing nature of colour creation between media.
Printers use Cyan, Magenta, Yellow and Black to simulate the full spectrum. This is known as the
subtractive method; remove all of these colours and you will end up with white (hence the
standard paper colour). Adding 100 percent cyan, magenta and yellow would, in theory, result in
black. However, in practice, results are never perfect, so printers include black ink; this is also a
more economical way to work.
Computer screens, along with other digital media such as scanners and digital cameras, replicate
colour using the additive method. Red, Green and Blue are combined to create a range of
millions of colours: Adding 100 percent of each colour results in white light, whereas 0 percent will
render black, in other words, no light.
If converting from a screen image to a printed version, all changes should be made in RGB mode
before a final conversion to CMYK, using the menu shown above. This will remove any colours that
can only be displayed on screen, replacing them with their nearest printable equivalents. If you
need to work on an image that has been saved in Indexed Color mode, you will need to convert it
to RGB Color in order for it to be fully editable. Indexed Color uses a smaller palette to cut down
on file size.
The advantage of working in RGB Color is that you have access to all the bells and whistles of
Photoshop which would otherwise be hidden or greyed out in CMYK Color.

Choosing an RGB working space

The colour working space refers to the gamut (range of colours) that can be displayed or printed.
This range varies for different RGB working spaces and for different devices and can be changed
in Photoshop.

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sRGB IEC-61966-2.1
sRGB is the standard colour space for PC computer monitors and is the colour space assumed by
many applications (including Web browsers and Photoshop). However, it has a limited gamut,
sufficient for on-screen use (e.g. Web design, PowerPoint presentations), but unsuitable for quality
printing, since it clips colours in the CMYK gamut.

Adobe RGB (1998)

Adobe RGB (1998) has become the recommended RGB editing space for RGB files that are
destined to be converted to CMYK for print output. It provides a much wider gamut and
consequently it has a much better ability to capture very deep or bright colours.
The figure on the right shows the full colour gamut (billions
of colours) visible to the human eye. A shows the typical
Adobe RGB (1998) colour space and B the sRGB colour
space.
As you can see, A covers a greater range of colours than
B.
There are other RGB colour spaces that have a much
wider gamut (Wide Gamut RGB), however, these are
intended for highly specialised applications.
To summarise, you should stick to sRGB for images
intended to be used on the Web or for on-screen
presentations, and convert to Adobe RGB (1998) for Chromatic
images intended for print (after conversion to CMYK) diagram

• To change the RGB colour space from sRGB to Adobe RGB, go to Edit/Color Settings. In the
Color Settings dialogue box, in the RGB drop-down menu (under Working Spaces) select
Adobe RGB (1998) as shown below:

• To convert from RGB mode to CMYK, go to Image/Mode and select CMYK Color from the
list.

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Monitor calibration
The Adobe Gamma utility comes bundled with Photoshop and can be used to calibrate a monitor’s
settings: RGB colour balance, brightness, contrast and white point (the point at which colour will be
displayed as white).
To launch the Adobe Gamma wizard, go to Settings/Control Panel and double-click on the icon
labelled Adobe Gamma.
The wizard will appear as follows:

Make sure the Step By Step (Wizard) radio button is checked and click the Next button to
proceed.
Leave the default monitor profile selected unless you know of a better match for your screen, in
which case click the load button and choose from the list displayed.
Click the Next button and follow the on-screen instructions to set the brightness and contrast of
the monitor.
Again, click Next to display the Phosphors pop-up. This should be left unchanged, unless you
know for certain that your monitor’s phosphors differ from the default option.
Proceed by clicking the Next button. Uncheck the View Single Gamma Only box and set the
gamma (mid-tone) brightness of your screen for each primary colour by following the on-screen
instructions.

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Introduction to digital imaging using Photoshop (photoshop-t1)

Assuming you are using a PC, from the dropdown menu, select Windows Default. There is also a
Macintosh option. The Custom setting is only available to Macintosh users.
Having clicked Next to continue, leave the Hardware White Point as displayed unless you know it
is incorrect. Continue to the next screen, leave Adjusted White Point as set and proceed to the
final screen. You have an option to view the screen with before and after settings, before clicking
the Finish button to name and store your monitor’s new profile.
See Ian Lyons’ article, Photoshop CS - Colour Management (www.computer-
darkroom.com/ps8_colour/ps8_1.htm) for a more detailed introduction to colour management.

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Task 1 Getting started

Objectives To open an image and learn to use some basic tools and menus.
Comments Cropping consists of selecting the area of an image that you want to keep and
eliminating what is deemed superfluous. It is probably the first thing you will want to
do to a photograph.

1.1 Start Photoshop and open an image:

¾ Go to Start/Programs/Web Graphics/Photoshop CS2/Adobe Photoshop CS2.
¾ Click No to the question ‘Do you want to customize your color management
settings now?’.
¾ Go to File / Open and in C:\User\Graphics\, open the file: egypt150.tif.
Note This image was scanned at a resolution of 150 dpi (dots per inch) at 100% of its
original size.
1.2 Make a copy of the image:
¾ Go to Image / Duplicate.
¾ Accept the suggested file name (egypt150 copy) and click on OK.
¾ Close the original image by clicking the Close icon in the top right corner of
the Image Window.
Note It is good practice to work on a copy rather than on the original version of a
photograph, so that you have a backup in case something goes wrong!

The View menu

1.3 The View menu contains various utilities that make working with Photoshop easier:
¾ Go to the View menu and select the following options (selected options have a tick
mark next to them):
• Rulers (it may already be selected) – to display rulers along the top and left
edge of the Document Window.
• Show / Grid – to display a grid on the image (grids are useful for aligning
elements).
To alter the grid spacing go to Edit / Preferences / Guides, Grids & Slices.
• Show / Guides – guides can then be positioned anywhere in the image area
and used for the precise positioning and alignment of image elements
Note You can switch grids and guides on and off by (de)selecting Extras in the View
menu, or using the keyboard shortcut <Ctrl> + H.
1.4 The ‘Snap to’ feature is particularly useful for precise aligning or positioning of image
elements (eg text, cropping marquee, etc):
¾ Go to View / Snap to to specify the elements (eg Guides, Grid, Document
bounds, etc) to which you want to snap when snapping is enabled.
Note However, sometimes snapping prevents you from correctly placing elements, so it is
important to be able to switch it on and off quickly. Use the keyboard shortcut <Ctrl>
+ <Shift> + ; to enable or disable snapping – alternatively go to View / Snap.

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The Document window

1.5 Change the ruler unit:
¾ Right-click anywhere on the left or top ruler to open the context menu and select a
different unit than the one selected – settle for Pixels in the end (Figure 1).

Right-click

Figure 1 - changing the ruler unit

1.6 Insert guides:

¾ Click and hold anywhere in the top ruler, and drag down the mouse cursor until you
see a horizontal blue line.
¾ Similarly, add a vertical guide starting in the left ruler and dragging to the right.
¾ To reposition a guide select the Move Tool in the Toolbox, then grab a guide and
move it up or down, or left or right.
Note To enable or disable guides quickly use the keyboard shortcut <Ctrl> + ;.

Figure 2 - scaled preview in the Status bar

1.7 The Status bar at the bottom of the Document window provides useful
information:
¾ Click anywhere in the status information box containing size / dimension etc
information, and keep the mouse button down.
¾ This will bring up a scaled preview showing the size and position the image will be
printed at with the current page setup (Figure 2).
Note To check or change the page setup, go to File / Page Setup. The default page
setup should be A4 portrait.
¾ Try the same thing but this time pressing the <Alt> key as you left-click in the status
information box. This will display the image dimensions, the colour mode and
resolution (Figure 3).

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Introduction to digital imaging using Photoshop (photoshop-t1)

Figure 3 - image information in the Status bar

¾ Finally, click on the arrow next to the status information box (Figure 4), select Show
and try the different options:

Status information options

Figure 4 - accessing the status information options

• Version Cue: a tool for working collaboratively on projects – not relevant to

most users.
• Document Sizes: the first figure shows the file size of a flattened version of the
image. The second, the size if saved with all the layers.
• Document Profile: the current profile (colour mode and pixel bit depth)
assigned to the image.
• Document Dimensions: the image dimensions expressed in the unit set for the
rulers.
• Scratch Sizes: the first figure displays the amount of RAM memory used. The
second shows the total RAM available to Photoshop.
• Efficiency: summarises how efficiently Photoshop is working.
• Timing: shows the time it took to complete the last operation. Reset every time
you change tools or execute a new operation.
• Current Tool: displays the name of the tool currently selected.
• 32-bit exposure: Option for adjusting the preview image for viewing 32-bits-per-
channel high dynamic range (HDR) images – not relevant to most users.

Zooming in and out of an image

1.8 Using the Zoom Tool:
¾ In the Toolbox select the Zoom Tool. As you hover the mouse pointer
over the image notice how it changes into a magnifying glass icon with a +
sign inside.
¾ To zoom in:
• either click on the image repeatedly until you reach the desired level of
magnification (up to 1600%),
• or drag the magnifying glass to delimit the area you wish to magnify.
¾ To zoom out, hold down the <Alt> key – notice how the plus sign in the
magnification glass icon changes to minus – and click on the image until you reach
the desired level of magnification (down to 0.4%).

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Task 2 Cropping and correcting perspective problems

Objectives To crop an image and straighten out keystone distortion.
Comments Cropping consists of selecting the area of an image that you want to keep and
eliminating the outer crop area. The Photoshop crop tool also allows you to correct
perspective problems (keystone distortion) such as the vanishing vertical edges of a
building photographed from ground level.

Simple cropping operation

2.1 Define the crop area:
¾ In the Toolbox select the Crop Tool.
¾ Click in the top left corner of the area you want to select and drag towards the
bottom right to mark out the area that you want to keep (crop marquee). Notice how
the area outside the crop selection dims.
¾ Adjust the crop marquee to cover an area similar to that in Figure 5:
• To scale the crop marquee grab and drag one of the handles – to constrain the
proportions, hold down <Shift> as you drag a corner handle.
• To reposition the crop marquee, place the cursor inside the marquee – it will
change to a black arrow – and drag.

Crop Tool handles

Figure 5 - the crop marquee in the image window

Note You can also rotate the crop marquee. Place the cursor just outside one of the
corners until it changes into a curved arrow, then click and drag. To move the centre
point around which the crop marquee is rotated, click and drag the centre point
around which the marquee rotates.

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2.2 Commit the crop:

¾ When you are satisfied with the position and size of the crop marquee, click
the Commit button, press <Enter>, double-click in the crop marquee, or
right-click and choose Crop from the context menu.
Note Until the cropping operation has been either committed or cancelled, no other
tool or menu can be used. To cancel the cropping operation, press <Esc> or
click the Cancel button in the Options bar.

Cropping with perspective correction

2.3 Define a new crop area:
¾ Undo your previous crop – either use Edit / Undo Crop, or the History palette.
¾ Define another crop marquee, this time making sure you include the vertical lines on
either side of the characters, as well as the horizontal line below their feet, as shown
in Figure 7.
2.4 Correct the keystone distortion:
¾ In the Options bar that appears at the top of the screen when you choose the Crop
Tool, tick the Perspective box (Figure 6).
Perspective tick box

Figure 6 - the crop tool option bar

¾ Click the top left corner handle and drag it to the right until the left marquee border is
parallel to the vertical line in the image.

Crop marquee line

Vertical line in the image

Figure 7 - correcting perspective

¾ Repeat, using the other corner handles to level the bottom and top horizontal
marquee borders with the horizontal lines in the image, and the right marquee
border with the right side vertical line in the image.
¾ Once you are satisfied with your selection, commit the crop.

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Your image should now have perfect vertical and horizontal lines, as illustrated in
Figure 8:

Figure 8 - cropped image after perspective correction

Note This operation can be fiddly, particularly with images that do not have clear vertical
and horizontal lines. Trial and error and a little patience should overcome any
difficulty!

Saving the cropped image

2.5 To save your image:
¾ Go to File / Save As.
¾ In the Save In box of the Save As window, go to C:\User\Graphics\, in the File
Name box replace the suggested file name with egypt_mural_before, and in the
Format box select TIFF(*.TIF).
¾ Click on Save.
¾ In the TIFF Options pop-up window, leave the options as they are and click on OK.

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Task 3 Adjusting overall tone and colour

Objectives To make basic image corrections using Photoshop’s image correction tools.
Comments Once you have cropped your image, the next thing you will want to do is improve its
appearance. For example it may lack contrast, have a colour cast, be too bright, or
display any combination of these faults.

3.1 Make a duplicate of your egypt_mural_before.tif image:

¾ Choose Image / Duplicate and rename the copy as egypt_mural_after.
¾ Close egypt_mural_before.tif.
Note Having a ‘before’ and ‘after’ image will enable you to compare your modified image
to the original later.

Interpreting an image
3.2 Before making any adjustment, it is important to be able to analyse the image you
are working on.
We can use our eyes to make subjective judgements about how the picture looks,
but for more useful and objective information we can also use the image histogram.
¾ In the Window menu, select Histogram. Then open the palette menu and select
Expanded View (see Figure 9 below):

Click here to open the

palette menu

Figure 9 - expanding the view of the Histogram palette

The Expanded View displays some extra options (Figure 10):

Channel menu

Refresh button
Number of pixels

Black (0) White (255)

Statistical information

Figure 10 - the Histogram palette Expanded View

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¾ The histogram shows the shades of tones (pixels) that make up an image as well as
their distribution for all 3 channels at once (RGB) or individual channels.
¾ What does the information provided by the Histogram palette tell you about the
current image?

Adjusting brightness and contrast with Levels

Note Open the Layers palette if it is not already open. Go to the Window menu and
select Layers.
3.3 Resetting the input shadow and highlight levels:
¾ At the bottom of the Layers palette, click on the Create new fill or
adjustment layer icon and select Levels to open the Levels dialogue box
(Figure 11):
Channel selector Gamma slider

Input shadow Input highlight

levels slider levels slider

Output highlight
levels slider

Output shadow
levels slider

Figure 11 - the levels dialogue box

Input Levels
• The Input Levels’ sliders and entry boxes allow you to increase the contrast by
adjusting the input shadows and highlights.
• The Gamma and entry box allow you to adjust the relative image brightness
between the shadows and highlights (drag the slider left to lighten and right to
darken the image).

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Output Levels
The Output Levels’ sliders allow you to reduce the tonal range (contrast) in an
image. It is best not to touch these because they inevitably result in loss of data in
the shadows and highlights – unless you deliberately want to reduce the output
contrast.
The histogram in Figure 11 shows that the image has limited contrast, in other
words we have no dark blacks or bright whites. So the first adjustment we are going
to make is to reset the darkest shadow and lightest highlight points for each of the
RGB colour channels:
¾ Make sure the Preview box in the bottom right is checked so you can see the
changes taking place.
¾ In the dropdown Channel selector, select Red.
¾ Holding down the <Alt> key, first drag the Shadows input slider to the right and set
it just before you see some shadow detail in the image. Then drag the Highlights
input slider to the left and set it just before you see some highlight detail.
¾ Repeat the previous step for the Green and Blue channels and click OK once you
are satisfied.
¾ Notice how these changes have affected the RGB histogram in the Histogram
palette (Figure 12):

Figure 12 - image histogram after Levels changes

¾ You should now have a better spread of pixel levels between shadows and
highlights, but notice how some information has been lost at some levels (hence the
comb-like effect).

Adjusting the colour balance with Levels

In the previous task, we used the composite RGB channel of the Levels
adjustments to correct the overall contrast of the image. We are now going to use
the same tool to correct colour casts.
¾ Re-open the Levels adjustment layer you created in the previous task by double-
clicking on its thumbnail in the Layers palette (Figure 13):

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Double-click on the
Levels layer thumbnail

Figure 13 - re-open the Levels layer

At this point you need to decide whether your image has a colour cast and if yes
which colour. So let’s say your picture looks too blue and you want to add more
yellow:
¾ Go to the Channel menu and select the Blue channel.
¾ Move the Gamma slider slightly to the right as in Figure 14:

Figure 14 - correcting a blue cast using Levels

If your image has a different colour cast, use the following table to decide which
channel to use:
Colour cast: Use the colour Move the Colour
channel: Gamma slider: added:
Red Red Right Cyan
Green Green Right Magenta
Blue Blue Right Yellow
Cyan Red Left Red
Magenta Green Left Green
Yellow Blue Left Blue

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Note When dealing with black and white photographs, you don’t need to adjust each
colour channel separately. To correct the overall contrast and brightness you can
use the composite RGB channel instead. Use the Input Levels to improve the
overall contrast, and then the Input Gamma to correct the brightness.

More colour adjustments with Hue/Saturation

3.4 The Hue/Saturation dialogue box allows you to adjust the hue (colour), saturation
(colour intensity), and lightness of the entire image or of individual colour
components in an image.
¾ Click on the Create new fill or adjustment layer icon at the bottom of the
Layers palette and select Hue / Saturation to open the corresponding
dialogue box (Figure 15):

Edit dropdown
options

Eyedroppers

Original input
colour ramp

Output colour
ramp

Figure 15 - the Hue/Saturation dialogue box

The two colour spectrum ramps at the bottom of the Hue/Saturation dialogue box
provide a visual clue as to how the colours are being mapped from one colour to
another.
The Edit dropdown menu at the top defaults to Master, which means any
adjustment will affect all the colours in an image. The other six options (eg Reds,
Greens, Blues, Cyans, etc.) allow you to narrow the Hue/Saturation adjustments
to predefined colour ranges. You can also redefine these ranges using the
eyedroppers or markers between the colour ramps.
¾ In the Edit dropdown menu box, select Reds to start with.
¾ Adjust the Hue, Saturation and Lightness by dragging the sliders left or right or by
entering a value in the corresponding box (-180 to +180 for Hue and –100 to +100
for Saturation and Lightness).
¾ Repeat with other colours – notice that some may have little effect, which indicates
that these colour ranges are not present in the image.
¾ Click OK once you are satisfied with the results.

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Task 4 Sharpening an image

Objectives To sharpen an image.
Comments Photoshop provides four sharpening filters – Sharpen, Sharpen More, Sharpen
Edges and Unsharp Mask. Unsharp Mask is the one that gives you the most
control.

¾ The Unsharp Mask works by increasing the contrast between pixels. Unlike tone
and colour adjustments, Unsharp Mask is applied to the Background layer (or
even better a copy of the Background layer), that is the layer containing the original
image.
4.1 Create a copy of the Background layer:
¾ In the Layers palette, drag the Background layer onto the Create a new
layer icon to make a copy of it. It will appear as a new layer as shown in
Figure 16:

Figure 16 - creating a copy of the Background layer

Creating a copy of your background image protects the original image because it is
easier to delete a layer rather than undo changes to the background image.
4.2 Sharpen the image:
¾ Make sure the Background copy layer is selected.
¾ In the Photoshop Filter menu, choose Sharpen / Unsharp Mask.
In the Unsharp Mask dialogue box (Figure 17) you can set three parameters:
• Amount controls the amount of sharpening applied to the edges (1% to 500%).
Values up to 50% produce subtle effect; values between 50% and 250% produce
moderate effects.
• Radius controls the depth of pixel along the high-contrast edges that are
changed. Values of up to 2.0 produce acceptable sharpening.
• Threshold sets a level for the minimum amount of contrast between pixels that
an area must have before it will be modified. Use a low value to apply the filter
more generally throughout the image.

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Figure 17 - the Unsharp Mask dialogue box

¾ Experiment with the different settings described above and observe the changes to
the image.
As a general rule, apply an amount of between 100% and 200%, a radius of
between 1.0 and 2.0, and a threshold of between 0 and 10.
Note Sharpening for output should be applied at the end of a Photoshop session and after
the image has been resized to the final print size.
4.3 Save a copy of your image in the Photoshop format.
¾ Go to File / Save As.
¾ In the Save In box of the Save As window, go to C:\User\Graphics\. In the File
Name box replace the suggested file name with egypt_mural_after, and in the
Format box select Photoshop(*.PSD,*.PDD).
¾ Click on Save.
Note The reason for saving in the Photoshop format is that it will preserve all the layers,
which will allow you to make further changes to them at a later stage.
4.4 Make a copy of egypt_mural_after.psd:
¾ Choose the Image / Duplicate command and accept the suggested name
egypt_mural_after copy.
¾ Close egypt_mural_after.psd.
4.5 You are now going to ‘flatten’ the image (that is, merge the layers) and save this
new file as a TIFF image.
¾ Click on the black pointed arrow in the top right hand corner of the Layers palette
and click on Flatten Image in the pop-up box (Figure 18):

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Click here to open the

Layers palette popup
menu.

Figure 18 - flattening an image

Note You could also use Flatten Image in the Layers menu.
¾ Go to File / Save As.
¾ In the Save In box of the Save As window, go to C:\User\Graphics\. In the File
Name box replace the suggested file name with egypt_mural_after, and in the
Format box select TIFF(*.TIF).
¾ Click on Save.
¾ In the TIFF Options pop-up window, make sure IBM PC is selected and that LZW
Compression is unchecked.
¾ Click on OK.

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Task 5 Resampling an image

Objectives To resize and/or resample an image.
Comments There are times when you will want to modify the size of an image. When preparing
an image for screen display, you do this by resampling – or interpolating – the
image.

5.1 Make a copy of egypt_mural_after.tif:

¾ Open egypt_mural_after.tif (it may already be opened).
¾ Make a copy of it using the Image/Duplicate command and give it the name
resample.
5.2 Set the rulers:
¾ In the View menu, select Rulers.
¾ Next, right-click anywhere on the ruler and select Pixels.
5.3 Prepare to resample the image:
¾ Go to Images / Image Size to open the Image Size dialogue box (Figure 19).

Figure 19 - the image size dialogue box

¾ Select Resample Image at the bottom if it is not already selected.

Note When Resample Image is selected, the Pixel Dimensions box, at the top,
becomes active. This allows you to change the pixel dimension of the image.
¾ Check that Constrain Proportions is also selected

Resampling up
Interpolating up is a process that consists of adding new information (pixels) to an
image in order to increase its dimensions or resolution, or both. The file size
increases as a consequence. This process is useful in cases where you cannot
rescan the original at the correct settings.
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5.4 Increasing the Pixel Dimensions of the image:

¾ Select Bicubic Smoother as the interpolation method from the drop-down list next
to the Resample Image check box.
Note Bicubic Smoother is the ideal choice when making the image bigger.
¾ If you want to increase the physical dimensions of the image without changing the
resolution, enter a higher value (for example 800) in the Pixel Dimensions Width
box.
Observe the changes in the Document Size options: the Width and Height have
increased, but the Resolution is unchanged.
¾ Click OK and look at your resampled image.
¾ Undo the changes that you have just made (Hint: use Edit / Undo Image Size).
5.5 Increasing the image Resolution:
¾ Return to Image / Image Size.
¾ If you want to increase the image resolution without changing its physical
dimensions, enter a higher value in the Resolution box (for example 300).
Observe the changes in the Pixel Dimensions options: the Width and Height have
increased accordingly.
Note There is a simple rule to help you calculate the relationship between pixel
dimension, resolution and physical dimension:
pixel dimension = physical dimension (inches/centimetres) x resolution (points per
inch/centimetre).
¾ Click on OK and look at your resampled image.
¾ Undo the changes that you have just made.
Warning! Resampling up is a compromise solution since all you do is add pixels to the image
without increasing the quality and detail. You may need to use the Unsharp Mask
filter to compensate for blurring, which may occur due to the interpolation process.
You will obtain better results if you can rescan the image at the right size and
resolution for its intended use.

Resampling down
Interpolating down consists of discarding pixels and results in a smaller file size.
There are two ways of achieving this: either by decreasing the resolution or by
decreasing the dimensions of the image.
5.6 The procedures are the same as for resampling up:
• If you want to reduce the file size and the total number of pixels while retaining
the physical dimensions, enter a lower value in the Resolution box.
• If you want to reduce the physical dimensions while keeping the same
resolution, enter a lower value in either the Document Size Width or Height
entry box.
Interpolating down is particularly useful when you want to create a thumbnail image
for a Web page.
Note A thumbnail is a small image that downloads quickly and can link to another page
containing the full size image. The advantage of using thumbnails for large images
is that users of your site can decide whether to view the larger images (and
therefore wait for them to download) or not.

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¾ Open the Image Size dialogue box again, make sure the Resample Image check
box is selected and select Bicubic Sharper from the dropdown list.
Note With Bicubic Sharper, the scaled down image will retain more detail and sharpness.
¾ Set the Pixel Dimensions Width to 150 and observe the changes to the Document
Size dimensions. Click on OK.
5.7 Save the thumbnail image:
¾ Go to File / Save As. Enter egypt_mural_thumbnail in the File name box and
choose JPEG (*.JPG; *.JPE) in the Format box. Make sure you are saving in
C:\User\Graphics\, and click on Save.
¾ In the JPEG Options dialogue box (Figure 20), move the Quality slider in Image
Options from small file to large file (alternatively you could use the entry box or
the dropdown menu).

Figure 20 - JPEG saving options

¾ Under Format Options, select Baseline ("Standard").

Note Baseline ("Standard") is the most universally understood JPEG format.
Baseline Optimised will often produce a slightly more compressed sized file, but
some web browsers may not be able to read it correctly.
Progressive creates a file that will download in an interlaced fashion – the image
downloads in a series of passes and appears blurry at first, until it gradually comes
into focus.
Notice the changes in the Size box at the bottom, it tells you how long your file will
take to download at different connection speeds – select 56.6Kbps, which is the
most common telephone modem connection speed.
¾ Settle for a high quality (for example 10) image and click on OK.
Note JPEG is a compressed format widely used for Web images. We cover image
formats in more detail in Task 6.

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Checking the print size of an image

You can also use the Image Size dialogue box to check the print size of an image at
different resolutions without resampling it.
¾ Reopen egypt_mural_after.tif if you closed it and go to Image / Image Size.
¾ In the Image Size dialogue box, uncheck the Resample Image option – the Pixel
Dimensions options will grey out and become un-editable (Figure 21):

Figure 21 - Image Size dialogue box with Resample Image option off

¾ Change the Resolution (for example try 225 and 300 pixels/inch) to see the
changes to the Document Size Width and Height. This is useful so that you can
check the size of a print out of your image at different resolutions.
¾ Go to File / Print with Preview to get an idea of the print size in relation to an A4
sheet of paper.
Note If you find image sizing confusing, use the Resize Image Assistant wizard located
in the Help menu to guide you. It can be used to resize images both for print and for
the web.

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Task 6 Optimising an image to a suitable format

Objectives To save an image in a suitable format for its intended purpose.
Comments There are many image/graphic file formats to choose from. However, you don’t need
to know them all. On this course you have used three different formats so far (TIFF,
Photoshop and JPEG). We will introduce a fourth one, GIF, which is a popular
format for screen display.

Let’s start with a brief summary of the four common file formats used on this course:
• TIFF: The most common cross-platform format for images. TIFF is the format of
choice for scanned images and archival purposes because it keeps all image
data intact. The downside is the large file size that makes it unsuitable for the
Web.
• PSD: PSD is Photoshop’s own file format. For flexibility in what you can do with
the file in the future (all layers are preserved), it’s a good idea to save a working
copy of your image in this format.
• JPEG: This is one of two standard compression formats used for preparing
images for the Web (the other one being GIF). It offers a smaller file size than
TIFF and is the format of choice to compress photographic images for the Web.
• GIF: This is the other image file format used for preparing images for the Web. It
is mostly used for saving logos, typography, etc. It is an 8-bit colour display mode
that indexes specific colours to each of the 256 (or fewer) numeric values.
6.1 Open your egypt_mural_after.tif again if it’s not already open.
¾ Go to File / Save for Web to open the Save For Web dialogue box (Figure 22) and
click on the 4-Up tab in the top left corner if necessary.
4-Up

Figure 22 - the save for web dialogue box

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Saving as a GIF
¾ In the 4-Up view, select one of the preview images and set the format to GIF (Figure
23)
Preset file format
dropdown
File format dropdown

Colour reduction
algorithm

Dither algorithm

Figure 23 - saving options for GIF format

¾ Try out the various options (Lossy, Colors, Dither, etc.) and observe the
changes to the GIF preview image – it may help if you zoom in using the
Zoom Tool in the top left.
Notice the changes to the file size at the bottom of the selected preview image as
you change the settings.

Saving as a JPEG
¾ Select the top right image and select JPEG from the format dropdown box (Figure
24):
Preset file format
dropdown
File format dropdown
Quality setting slider

Quality setting
dropdown

Figure 24 - saving options for JPEG format

¾ Then set the quality to Maximum (100).

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¾ Select the bottom left image, then select JPEG as format and set the quality to High
(60).
¾ Repeat for the bottom right image, setting the quality to Low (10).
Notice that the more compressed the image is, the lower the quality, file size and
download time:
Format File size Download time
TIFF 794K N/A
JPEG Maximum quality 336.5K 62s @ 56.6Kps
JPEG High quality 81.47K 16s @ 56.6Kps
JPEG Low quality 22.41K 5s @56.6Kps
¾ Use the Zoom Tool in the top left corner to magnify the four images and compare
the differences in quality.
You can probably see that there is not that much difference in quality between the
original image, the JPEG 100 quality and the JPEG 60 quality. For this reason, if
file size and download time are important criteria then the JPEG 60 quality would
be a good option. If quality were the most important criterion, then you would
optimise your image at Maximum quality.

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Task 7 Retouching a damaged photograph

Objectives To remove scratches and dust spots from an image.
Comments Old or neglected photographs often suffer from a variety of defects (scratches, dust
spots, creases, etc) that devalue them. Photoshop provides a range of tools to
correct these defects and with a little bit of practice it is easy to repair damaged
images.

7.1 Open a new image:

¾ Go to File / Open and in C:\User\Graphics\, open the file old_image_before.jpg
and make a copy of it using the Image / Duplicate command.
¾ Replace the suggested name with old_image_after and close
old_image_before.jpg.

Applying the Dust & Scratches filter to the whole image

7.2 Create a copy of the Background layer as described in task 4.1 (p. 22):
You should now have a Background copy layer above your original Background
layer.
7.3 Remove dust and scratches:
¾ Make sure the newly created Background copy layer is selected in the Layers
palette.
¾ Go to Filter / Noise / Dust & Scratches to open the Dust & Scratches dialogue
box (Figure 25):

Figure 25 - the Dust & Scratches dialogue box

¾ Make sure the Radius and Threshold sliders are all the way to the left to start with.

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¾ Slowly move the Radius slider to the right and observe the changes: the spots
disappear, but the image loses its inherent noise or film grain. Settle for a value of 6
pixels.
¾ Now move the Threshold slider to the right until the spots begin to reappear. Settle
for a value of around 25 levels and click on OK.
Note The degree of success you have with the Dust & Scratches filter depends largely
on the image or selection to which you apply it.

Applying the Dust & Scratches filter selectively

7.4 Although the spots and scratches are mostly gone and the grain restored, you will
probably notice that some of the important detail has been eliminated. This is
because the Dust & Scratches filter can’t tell the difference between a scratch and
an eyelash!
To remedy this problem, we’ll use a Layer Mask to hide the filtered image and then
'burn holes' in it to apply the filter only to the damaged areas of the image.
¾ Go to Layer / Layer Mask / Hide All. You should see a new, black-filled Layer
Mask in the Layers palette (Figure 26):

Layer mask thumbnail

Figure 26 - new layer mask in the Layers palette

¾ Make sure the Layer Mask thumbnail is active (it should be framed within a double-
line border); click on it if it’s not.
¾ Make sure foreground colour is set to white in the Set foreground/
background color tools located in the Toolbox (use the double arrow in
the top right corner to inverse foreground and background, if necessary).
¾ In the Toolbox, choose the Brush Tool and in the Options bar at the top
of the screen, set Opacity and Flow to 100% (Figure 27).

Figure 27 - the Brush Tool option bar Brush Preset picker

¾ Click the triangle next to the Brush Preset picker and choose a soft-edged brush
tip about the size of the specks you need to hide (about 17 px).
¾ Dab with the Brush Tool where you see specks in the image.
Notice the changes on the Layer Mask thumbnail in the Layers palette.
Note The dabs are like burning little white holes in the mask, allowing the filtered image to
cover the spots in those areas.

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Using the Clone Tool to correct the remaining blemishes

7.5 Next you will add a “repairs” layer above the filtered layer, where you can make your
“hand-painted” alterations. This protects the image from painting mistakes and also
makes it easy to make changes to your repairs later if you need to.
¾ Add another layer by clicking on the Create a new layer icon at the bottom
of the Layers palette.
¾ Choose the Clone Stamp Tool in the Toolbox, and in the Options bar set
the Opacity low (for example 30%) and select the Sample All Layers
check box (Figure 28).
Brush Preset picker

Figure 28 - the Clone Stamp Tool options bar

¾ Click the triangle next to the Brush Preset picker and choose a soft-edge brush tip
(for example, 17 px) about the size of the specks you need to hide.
¾ To start the repairs, hold down the <Alt> key and click in an area near the flaw you
want the repair to sample from. Release the <Alt> key and move the cursor over to
the point where you want to clone to and click, several times if necessary, to cover
the flaw.
Note The Clone Stamp Tool works by sampling colours in an area and copying (cloning)
them to a damaged area. This is a fiddly job which requires frequent sampling, but
which can ultimately give excellent results.

Adjusting contrast and sharpening

7.6 Finally, you could refine your image by adjusting tone, colours and sharpening using
the methods described in Tasks 3 and 4.
For this task, we are simply going to apply a “quick fix” to adjust the image contrast.
¾ Click the Create new adjustment layer icon at the bottom of the Layers
palette and choose Levels.
¾ Click on Auto and then click on OK.
7.7 Save your image:
¾ Go to File / Save As.
¾ In the Save As dialogue box, navigate to:
C:\User\Graphics\.
¾ Save your file as old_image_after as a JPEG with maximum quality.
7.8 Open old_image_before.jpg to compare it side by side with old_image_after.jpg.
Observe the differences.

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Task 8 Working with selections

Objectives To select part of an image and discard what you don’t want to keep, or manipulate
the selected area.
Comments Selecting parts of an image is an essential skill in Photoshop. It is often the starting
point for further manipulations, such as combining images together and applying
filters/effects or making tonal adjustments to part rather than all of the image/layer
that you are working on.

Selections using the Marquee Tool

To “frame” a selection with a clear geometrical shape, you can use either the
Rectangular or Elliptical Marquee Tool.
8.1 Select part of an image with the Marquee Tool:
¾ Open the photograph manneken_pis.jpg in C:\User\Graphics\ and duplicate it
(Image/Duplicate).
¾ In the Toolbox, right-click on the Rectangular Marquee Tool (right) and
select the Elliptical Marquee Tool.
¾ Select an area of the image (for example the head of the statue) – it is easier to
select from top-left to bottom-right.
TIP: Hold down the <Shift> key as you draw your marquee, to obtain a circular or
square shape, rather than an elliptical or rectangular shape.
¾ Reposition your selection if necessary by clicking inside it and dragging to a new
position.
Note You can add to selections by holding down <Shift>, or subtract from a selection by
holding down <Alt> (alternatively you can use the Add to selection or Subtract
from selection buttons in the Options bar – see Figure 29).
¾ Experiment using the Add to selection, Subtract from selection options,
modifying the feathering (Figure 29) and using the Rectangular Marquee Tool if
you want.
Add to selection Subtract from selection
New selection Intersect with selection

Figure 29 - the Marquee Tool Options bar

Note Feathering creates a soft edged border around the selection that blends gradually
into the background. This technique is known as vignetting.
8.2 Use your final selection to create a vignette image:
¾ Using the Set foreground / background color tools located in the Toolbox, set the
background colour to white or black.
¾ Go to the Select menu and choose Inverse – this will inverse the selection so that
the area outside your selection becomes selected (notice the marching ants around
the edges of the image).
¾ Press the <Delete> key to get rid of the inversed selection area. You should be left
with a cut-out of the statue blending smoothly with a black or white background.

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¾ Close these images without saving.

Selections using the Magic Wand Tool

The Magic Wand allows selections by colour-matching. It is particularly useful when
selecting an area containing pixels whose luminosity values are close, such as a
blue sky for example.
8.3 Select part of an image with the Magic Wand:
¾ Open the photograph willstower.jpg in C:\User\Graphics\ and duplicate it
(Image/Duplicate).
¾ In the Toolbox, select the Magic Wand Tool.
¾ In the Options bar, select the Add to Selection option (Figure 30):

Add to selection

Figure 30 - the Magic Wand Tool Options bar

¾ Set Tolerance to 1 and make sure Contiguous is checked.

Note The Tolerance option controls the range of pixels that will be included in the
selection on either side of the pixel you click on. The Contiguous option only allows
neighbouring areas to be selected. If it is unchecked, similar colours in unrelated
parts of the image will also be selected.
¾ Click four or five times in different parts of the blue sky area, noting the low
tolerance. Change the tolerance to 10 and continue; you will notice that the whole
sky soon becomes selected, outlined by a marquee (Figure 31):

Figure 31 - sky selected using the Magic Wand Tool

8.4 Add a gradient to the selection:

¾ In the Toolbox, select the Gradient Tool – if it is not displayed, right-click
on the Paint Bucket Tool and select it from the list.

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¾ Referring to the Tool Options bar, near the top of the screen, make sure Linear
Gradient is selected (Figure 32):
Linear Gradient

Figure 32 - the Gradient Tool Options bar

¾ In the Toolbox, click the Set foreground color square to launch the Color Picker
palette. For optimum flexibility, ensure that the option Only Web Colors is
unchecked. Choose a medium dark to dark colour and click OK.
¾ Repeat for the Set background color square, this time choosing a lighter shade of
the colour you selected for the foreground.
¾ Place the cursor against the left-hand side edge of the blue selection and, holding
down the left mouse button, drag the cursor in a straight line to the right edge of the
sky and release.
You will notice that a gradient has been applied, but only to the selected area. If you
are unhappy with the result, you can simply drag a new gradient over the selected
area.
¾ Click <Ctrl> + D to deselect the sky – alternatively, go to Select / Deselect.
¾ Close the image without saving.

Selections using the Quick Mask mode

Working in the Quick Mask mode, you can isolate an area by painting over it.
8.5 Select part of an image in Quick Mask mode:
¾ Open the photograph hockey.jpg in C:\User\Graphics\.
¾ Select the Edit in Quick Mask Mode icon, situated below the
foreground/background colour picker (Figure 33).

Edit in Standard Mode

Edit in Quick Mask Mode

Figure 33 - Standard/Quick Mask Mode icons

¾ Select Brush Tool from the Toolbox.

¾ Click the Brush Preset picker in the options bar (Figure 34):

Figure 34 - the Brush Tool Options bar Brush Preset picker

¾ The Brush Preset picker displays brushes varying in hardness and diameter.
Choose a hard brush (indicated by a sharp circle), and set the size to 16.
¾ Paint over the area you wish to select, in this case the middle hockey player (ignore
the hockey stick).
Note how the selected area is highlighted in semi-transparent red (Figure 35):

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Figure 35 - Quick Mask applied to middle hockey player

¾ When you have finished, revert to the Edit in Standard Mode (see Figure 33) –
notice the marquee (marching ants) around the hockey player and around the edges
of the image.
¾ If necessary, tidy up the edges by returning to Edit in Quick Mask Mode, using the
Brush Tool to add to, and the Eraser Tool to subtract from the selection.
¾ Once you are happy with your selection, make sure you return to Edit in Standard
Mode and in the Select menu, choose Inverse.
8.6 Create a simple photo montage:
¾ Open the photograph royalfort.jpg in C:\User\Graphics\.
¾ Return to image hockey.jpg and, having selected the Move Tool, place
the cursor on the highlighted hockey player and drag the selection on to
the Royal Fort image. A new, independent layer will be created.
¾ Position the hockey player where you want it on the Royal Fort image.
¾ Check that the top layer containing the hockey player is highlightd in the
Layers palette. Select the Clone Stamp Tool and in the Options bar set
Opacity to 100%, Flow to 68%, and make sure the box labelled Sample
All Layers is checked.
¾ ‘Clone’ the flowers surrounding the hockey player, and use them to paint over the
join in the images (see task 7.5).
¾ If any traces of hockey stick are visible in the player’s hand, try using the same
technique to remove them.
¾ Save the image as success.psd in C:\User\Graphics\.

Selections using the Lasso Tool

The Lasso Tool is useful for selecting irregular shapes. There are three versions,
which come under one icon in the Toolbox:
• The default Lasso Tool is a free-hand tool useful to select very detailed
edges and requires a good deal of practice and patience! To use it,
hold down the left mouse button and drag a line around the desired
area. Then release to make the selection.

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• The Polygonal Lasso Tool enables you to select a series of short,

straight line segments, which makes it better to select shapes with a
smoother edge. To use it, click the left mouse button once and move
the mouse around the image, clicking each time you change direction. A series of
nodes will be created to join the lines. When you arrive back at the starting point,
click on the first node to create the selection.
• The Magnetic Lasso Tool has as sensing area (that can be changed
in the Options bar). When you move the cursor along the edges in a
picture, the Magnetic Lasso can sense where that edge is and create
a selection that follows it. It is probably the most useful of the three lasso tools.
8.7 Make a selection with the Magnetic Lasso Tool:
¾ Open the image autumnleaf.jpg in C:\User\Graphics\.
¾ Select the Magnetic Lasso Tool (right-click on the Lasso Tool icon in the Toolbox
and choose Magnetic Lasso Tool).
¾ In the Options bar, set Feather to 5 px and accept the default Anti-alias, Width,
Edge contrast and Frequency options (Figure 36):

Figure 36 - Magnetic Lasso Tool Options bar

Note You can change the settings in the options bar for the Magnetic Lasso Tool:
Feather (see second Note in task 8.1), Anti-alias smoothes the jagged edges of a
selection, Width sets the radius of the area where the tool looks for the edge, Edge
Contrast specifies how much contrast the tool should look for in finding the edge
and Frequency specifies how often locking points are laid down.
¾ Place the cursor anywhere on the edge of the main leaf, release the mouse button
and drag the cursor around the leaf – notice how the tool automatically follows the
edge created by colour or tone contrast.
¾ If you make a mistake, just press <Delete> to undo a segment. Where there is no
contrast for the Magnetic Lasso Tool to follow, regularly click on the edge to
increase the frequency of locking points.
¾ When you have come full circle, click the node at the starting point to make the
selection.
¾ From the main menu choose Select / Inverse and press the <Delete> key. This will
leave the selection set against a transparent background.
¾ Close the image without saving.

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Task 9 Blending images

Objectives To merge images together in a smooth transition.
Comments This technique is ideal for creating seamless photomontages.

Creating a new document

9.1 Create a new file:
¾ Go to File / New. In the New dialogue box, give your new image a name (eg
firstmontage). Set the Width to 300 pixels and Height to 100 pixels, the Color
Mode to RGB Color and Background Contents to White (Figure 37):

Figure 37 - New file dialogue box

9.2 Move images to the new document:

¾ Open the images library.jpg located in C:\User\Graphics\.
¾ Using the Move Tool, drag the image library.jpg on to the new blank
image.
Notice that a new layer containing the image has been created above the white
Background layer.
Note If rulers are not displayed, click View / Rulers. Right-click somewhere inside the
ruler and set the unit of measurement to Pixels.
9.3 Resize the image to make it smaller:
¾ Ensure the top layer is selected in the Layers palette. In the Edit menu, select
Transform / Scale.
This will display sizing handles around the image – if you cannot see the handles,
you can increase the canvas size by dragging its edges.
¾ Hold down <Shift> to preserve the aspect ratio, and move the corner points inwards
until you can see enough of the student in the image.

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As you do this, you can reposition the image by placing the cursor inside the
transform boundaries, pressing the left mouse button and dragging. Drag the image
to the right of the canvas, leaving approximately 1/3 of the canvas uncovered and
experiment with vertical alignment until you are happy with the position of the
student (see Figure 38):

Figure 38 - scaling down and positioning the library image

¾ Click <Enter> to commit the change – at this point, you can reposition the image if
you wish.
Note If the image keeps snapping to edges of the canvas, turn the Snap feature off by
selecting View / Snap and making sure the Snap option is unchecked. Repeat this
process to reset it if required.
9.4 Repeat steps 9.1 to 9.3 with the image computer.jpg, aligning it left, overlapping
the library image. It should cover just over ½ the canvas (see Figure 39):

Figure 39 - two overlapping layers

Note It is important that the images overlap sufficiently for the blending effect to work.

Blending the images

9.5 Blend the images as follows:
¾ Make a note of the computer image’s right edge on the horizontal ruler (around 150
to 170 pixels), and in the Layers palette, make sure Layer 2 (the computer image)
is selected.
¾ Then in the menu bar at the top, go to Layer / Layer Mask / Hide All to add a layer
mask.
You should now see the Layer Mask as illustrated in Figure 40:
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Figure 40 - Layer Mask applied to top layer

This renders the layer invisible, indicated by a black thumbnail in the layers palette.
Various tools can be used to ‘paint the layer back’. In this case, the
Gradient Tool is used to achieve a smooth transition from transparent to
fully visible.
¾ Having made sure the foreground colour is set to black, select the
Gradient Tool – if you can’t see it, right-click on the Paint Bucket Tool
and select it.
¾ Place the cursor just inside the right-hand edge of the computer image (refer to the
note you made earlier), roughly in the middle vertically. Click, hold down the left
mouse button and drag the mouse to the left, in a straight, horizontal line, stopping
just on the left edge of the library image, and release.
You will notice the computer image gradually appearing. The image becomes 100%
visible at the point at which the mouse is released. You will notice that the black
thumbnail now displays the applied gradient.

Figure 41 - Layer Mask after the Gradient Tool has been applied to it

If you are unhappy with your gradient, simply click and drag the mouse again. The
shorter the drag, the less gradual the transition between invisible and opaque.
Your blended image should look something like Figure 42:

Figure 42 - Layers gradually blended together

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9.6 Merge the two layers:

¾ In the Layers palette, select one of the image layers, press <Shift> and select the
other image layer.
¾ With the two image layers selected, click on the Link layers icon at the bottom of
the Layers palette (Figure 43):

Link layers icon

Figure 43 - linking the two image layers

Notice the link symbol is now displayed to the right of each image layer, indicating
that these layers are linked.
Note Linking layers is particularly useful when you want to apply the same changes (eg
repositioning, styles, etc.) to several layers.
¾ In the Layers menu, select Merge Layers. As a result, the two linked layers will
become one (Figure 44):

Figure 44 - merged linked image layers

¾ Save the image as firstmontage.psd in C:\User\Graphics\.

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Task 10 Working with text layers

Objectives To add and manipulate text layers.
Comments You can create type (text) anywhere in an image in Photoshop. When you create
type, a new type layer is added to the Layers palette. You can then manipulate it
like any other object (image, shape, selection, etc), and the text itself will remain
editable.

Preparing the text background image

10.1 In order to work as a background for text, the photo needs to be less opaque. A
background colour needs to be set, to bleed through as the image transparency
increases:
¾ In the Toolbox, click on the Set foreground color square and choose a fairly dark
colour.
In the Layers palette:
¾ Select the Background layer (currently white) and use the Paint Bucket Tool to
flood fill the whole canvas.
¾ Next, select Layer 2 (i.e. the photo montage) and click the Opacity settings triangle
at the top right of the Layers palette (Figure 45):
Set layer opacity

Figure 45 - changing the opacity level of a layer

Moving the slider to the left will gradually reveal the background layer. Set opacity
between 30% and 50%.
You should now have a suitable background for your text.

Adding text
10.2 Add some text:
¾ In the Toolbox, select Type Tool and click somewhere in the image. Note
that a new layer appears in the Layers palette.
¾ In the Type Tool Option bar (Figure 46) click on the Set the text color option and
pick a light colour for your text:
Toggle the Character and Paragraph palettes

Figure 46 - the Type Tool Options bar

Set the text color Create warped text

¾ Choose a font, style, size and anti-aliasing method from the font options (for
example Arial, 18pt, Bold, Sharp).
Note Anti-aliasing smoothes jagged edges by adding shading or colours.

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Note Working at different image resolutions will result in variations in apparent text size.
For example text will appear much smaller in a 300dpi image than in a 72dpi (typical
screen display resolution) image.
¾ Type Information Services, press <Enter> to start a new line and type Open Day.
10.3 Edit and position the text:
¾ Make sure the Type Tool is selected in the Toolbox and highlight the second line of
text.
¾ Using the Set the text color picker, choose a new colour and, when you are happy
with your choice, deselect the text by clicking outside it.
¾ Use the Move Tool to position your text on the canvas.

Enhancing the text

Several effects can be added to the text. A subtle drop-shadow can add definition
when text is set over a slightly ‘busy’ background.
10.4 Add a drop-shadow:
¾ In the Layers palette, make sure the Type layer is selected and click the Add a
layer style icon at the bottom (Figure 47):

Add a layer style icon

Figure 47 - the Type layer in the Layers palette

¾ From the pop-up menu, select Drop Shadow. This will launch the drop shadow
options palette, adding a default shadow to the text.
¾ Experiment with the Structure options (Blend Mode, Colour, Opacity, Angle,
Distance, Spread and Size) and click the OK button when you are happy.
Note Layer styles are applied to every object within a layer.
Your image should now be similar to Figure 48:

Figure 48 - banner comprising text over background image

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¾ When you are happy with your image, save as firstmontage.psd in

C:\User\Graphics\. By saving in this format, text will remain editable.
10.5 Save a copy for the Web (see Task 6.1). As the image includes photographs, the file
should be saved as a JPEG.
Note Further text editing is possible via the Paragraph and Character palettes (open by
clicking the Toggle the Character and Paragraph palettes icon on the Type Tool
Options bar. By default, the palettes are bundled together. Toggle between them by
clicking the labelled tabs. The Paragraph palette enables line spacing, alignment
and so on to be set. The Character palette provides a shortcut to several formatting
elements also found elsewhere (anti-aliasing, font colour, font size etc.)

You can also warp text in many different ways by using the Create warped text
option. Feel free to try these out.

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Appendix A Resolution and image size for printing

Print size at:
Pixel size Megapixels RGB size CMYK size 150 ppi 300 ppi
(MB) (MB)
1600 x 1200 2 6 7.5 11 x 8 inch 5.5 x 4 inch
(28 x 20 cm) (14 x 10 cm)
2400 x 1800 4.3 12.5 16.5 16 x 12 inch 8 x 6 inch
(40 x 30 cm) (20 x 15 cm)
3000 x 2000 6 17.5 23.5 20 x 13 inch 10 x 6.5 inch
(51 x 33 cm) (25 x 16.5 cm)
3500 x 2500 8.75 25 33.5 23 x 17 inch 11.5 x 8.5 inch
(58.5 x 43 cm) (29 x 21.5 cm)
Table 1 – Comparison of pixel resolution, megapixels, megabyte file size and print output
dimensions at different resolutions in inches (and centimetres)

Output use Screen ruling x 1.5 Standard quality x 2 High quality

output resolution output resolution
Newspaper 65 – 100 lpi 97 – 150 ppi 130 – 200 ppi
Books 120 – 150 lpi 160 – 225 ppi 240 – 300 ppi
Colour magazine 150 – 175 lpi 225 – 262 ppi 300 – 350 ppi
Art book/magazine 175 – 250 lpi 262 – 375 ppi 300 – 500 ppi
Photo quality inkjet printer 150 – 300 lpi 225 – 450 ppi 300 – 600 ppi
Table 2 – Rule of thumb screen resolutions for common print devices at lpi x 1.5 and x 2
quality factors

Example
Say you want to print a high quality A4 photograph on an inkjet printer:
A4 size = Width 8.268 x Length 11.693 inches (21 x 29.7 cm)
Printer resolution = 200 lpi
Quality factor = x 1.5
Print length x Printer resolution x Quality factor = number of pixels required in length
11.693 x 200 x 1.5 ≈ 3500 pixels in length
Print width x Printer resolution x Quality factor = number of pixels required in width
8.268 x 200 x 1.5 ≈ 2480 pixels in width

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Appendix B Further resources

General information
TASI (Technical Advisory Service for Images) – http://www.tasi.ac.uk
The advice section is highly informative. Any questions that you may have regarding
all stages of image digitisation will be answered. The sub-section entitled ‘Creating
Digital Images’ is particularly relevant to this course.
Internet for Digital Photography – http://www.vts.rdn.ac.uk/acl/tutorial/digiphoto

Scanning
Apart from the TASI website, you may find the following site very useful for all
scanning issues:
A few scanning tips, by Wayne Fulton – http://www.scantips.com

Photoshop tutorials
These tutorials cover most things you can do in Photoshop, including some useful
tutorials on image enhancement and restoration:
Adobe’s Photoshop tutorials – http://www.adobe.com/products/tips/photoshop.html
Janee’s Photoshop tutorials – http://myjanee.home.insightbb.com/tutorials.htm
‘Computer Arts’ Photoshop tutorials – http://www.computerarts.co.uk/tutorials/2d/

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