Digital images CS5 (PDF - 2.2MB) - University of Birmingham Intranet

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Centre for Learning and Academic Development
IT Training
Editing Digital Images with
Photoshop CS5
www.skills.bham.ac.uk
Editing Digital Images with Photoshop
CS5
Author: Phil Smith, based on previous material by Duncan
Greenhill
Version: 1.0, December 2010
© 2010 The University of Birmingham
All rights reserved; no part of this publication may be photocopied,
recorded or otherwise reproduced, stored in a retrieval system or
transmitted in any form by any electrical or mechanical means
without permission of the copyright holder.
Trademarks: Microsoft Windows and Adobe Photoshop are
registered trademarks. All brand names and product names used in
this handbook are trademarks, registered trademarks, or trade
names of their respective holders.
Contents
Editing Digital Images with Photoshop CS5 ............................................................. ii
About the workbook............................................................................................... 1
Editing Programs .................................................................................................... 2
Image basics ........................................................................................................... 3
Image Size ......................................................................................................................3
Image Resolution ...........................................................................................................3
Resolution for the Web ..................................................................................................................3
Using the Units Appropriately ......................................................................................................4
File Formats ...................................................................................................................4
Choose a non-proprietary open 'standard' ...................................................................................4
File formats for desktop printing.....................................................................................5
File formats for web delivery ..........................................................................................5
Starting Photoshop ................................................................................................. 6
The Screen.............................................................................................................. 7
Opening an image ..........................................................................................................7
Creating a new image .....................................................................................................7
The New Image dialogue box .......................................................................................................7
The Tools Palette............................................................................................................8
Extended Tools .............................................................................................................................8
The Options Bar .............................................................................................................9
The Marquee tool Option Bar .........................................................................................9
Panels and Workspace....................................................................................................9
Zooming.........................................................................................................................9
Selection tools.............................................................................................................. 10
Choosing the correct tool ........................................................................................................... 10
Quick Selection Tool ................................................................................................................... 11
Magic Wand Tool ....................................................................................................................... 11
The Lasso Tools .......................................................................................................................... 12
Feather and Anti-Alias ................................................................................................................ 13
Feathering ....................................................................................................................................13
Anti-aliasing ..................................................................................................................................14
Constraining selections .............................................................................................................. 14
Modifying selections .................................................................................................................. 14
Viewing multiple images............................................................................................... 15
Copying and Moving ..................................................................................................... 15
Transforming a Selection ............................................................................................................ 16
Cropping an image ....................................................................................................... 17
Editing Digital Images with Photoshop CS5
Page i
Correcting editing mistakes .......................................................................................... 17
Layers ................................................................................................................... 19
The Layers Palette ........................................................................................................ 20
Editing layers.............................................................................................................................. 20
Layer Blending Modes ................................................................................................................ 21
Correcting and Enhancing Photographs ................................................................. 22
Brightness/Contrast ..................................................................................................... 22
Colour Levels and Colour Curves ................................................................................... 23
Photo Filter .................................................................................................................. 24
Using Black & White ..................................................................................................... 24
Red Eye Removal .......................................................................................................... 25
Blur .............................................................................................................................. 25
Filter Gallery ................................................................................................................ 26
The Type Tool............................................................................................................... 27
Character Options ...................................................................................................................... 27
Images for the Web .............................................................................................. 28
Appendices........................................................................................................... 30
Full List of tools available from Tools Palette ................................................................. 30
University Communications Guidelines ......................................................................... 30
Page ii
About the workbook
The workbook is designed as a reference for you to use after the
course has finished. The workbook is yours to take away with you
so feel free to make any notes you need in the workbook itself
The workbook is divided into sections with each section
explaining about a particular feature of the program or how to do
a particular task. Sections that take you through a particular
procedure step-by-step look like this:
How to do something
Do this first.
Then do this.
Then do this to finish.
There are also a number of text boxes to watch out for
throughout the workbook. These will help you to get the most out
of the course.
Tip
The thumbs up symbol in the margin indicates a tip. These tips will help you
work more effectively.
Danger!
The thumbs-down picture in the margin indicates common mistakes or
pitfalls to be avoided.
Page 1
Editing Programs
There are many image editing programs. Some, such as the
paint program that comes with Microsoft Windows, are very
basic. Some, such as the industry-standard Photoshop, are rich
in features, and there are a variety of programs that fall
somewhere between the two extremes.
When it comes to choosing the right software for you, it will
usually come down to a basic choice of cost versus features.
However, there are now many ‘open source’ programs that are
available for free to download via the internet. These programs
can be very extensive and feature-heavy, and are either entirely
free or free for a basic version with the possibility of upgrading to
a paid extended version.
Other questions worth asking are regarding hardware
requirements and functionality. Some of the more feature-heavy
programs (such as Photoshop) require fast processors and large
hard disks to accommodate all of their functions. Do make sure
that your PC is able to run this software before purchasing.
Regarding functionality, some features, such as file formats and
layers, may not be supported by some of the basic, lower-end
programs. Again, do make sure that any features that you have
already used or wish to use are supported by your chosen
program.
It is also worthwhile to note that support within the university via
helpdesk or the IT Training team can only be provided for
Photoshop, and not the open source programs. Below is a table
with examples of the various software programs and where you
should be able to obtain them:
COST
SOURCE
Adobe Photoshop CS5
TITLE
£160.93
http://www.softwaresales.bham.ac.uk/az/
adobe.shtml
Adobe Photoshop Elements 8.0
£41.65
adobe.shtml
Paint Shop Pro X3
£54.00
paintshoppro.shtml
Paint.NET
FREE
http://www.getpaint.net/
Picasa
FREE
http://picasa.google.co.uk/
GIMP
FREE
http://www.gimp.org/
Picnik
FREE
http://www.picnik.com/
Prices correct as of September 2010
Page 2
Image basics
Before we begin, we need to explore some basics that we need
to consider when using digital images. These mainly concern
image size, image resolution and file formats.
For the purposes of this introductory course I shall aim to keep
things relatively simple and straightforward, however, at the end
of the booklet I shall provide some sources for if you wish to
explore these areas yourself more thoroughly.
Image Size
The size of a digital image can be determined in two ways.
When the image is being used on the screen it is determined by
the number of pixels (vertical and horizontal), that are used in the
image. For printed output, the physical size of the image is only
dependent upon the constraints of the output device.
Image Resolution
Resolution within digital imaging is a highly misunderstood topic.
It should first be remembered that digital images themselves
have no size other than the number of pixels that they contain.
The image only has a 'real-world' size (inches or centimetres)
when it is in an analogue form before digitisation or after output.
Resolution for the Web
In many cases the Web user's monitor settings cannot be known.
An image that will look acceptable on a range of settings should
be created to ensure that sufficient information is communicated
to every user.
A much used technique, which saves space on screen, is to
display a small, low resolution copy of a graphic (thumbnail) in a
Web page which is linked to a higher resolution copy. When a
user clicks the thumbnail the larger, higher resolution image is
displayed in the browser.
ppi -
pixels per inch
'ppi' is used to describe the resolution of the image when it is in
its 'virtual' state. Once the digital image is in the computer it has
entered the 'virtual world' and has no 'real world' size until
rendered by an output device that translates the 'virtual' digital
image into a 'real world' image.
In the 'virtual world' any given resolution is only a guide for how
the image might be output. This has no effect on the size or
quality of the image itself, e.g. an image with 800 pixels in it's
length could be 2in at 400ppi or 8in at 100ppi, however the digital
image would be identical in both cases.
Page 3
When a 'virtual' digital image is output onto a monitor there is a
one-to-one mapping from pixel to 'monitor dot' and we therefore
also measure this in 'ppi'. Typically this used to be 72ppi with old
monitors but these days is more likely to be as much as 92-96ppi.
lpi - lines
per inch
When we print an image out its 'real world' size will be dependent
on the resolution of the printer. This resolution measurement is
described by the number of printed half-tone lines per inch (lpi)
that the printer uses. Typical resolutions for this would be from
85 lpi for newsprint to 200 lpi for an art magazine.
dpi - dots
per inch
It has become known and accepted as a generic 'catch-all' unit
that the printing industry uses to encompass all the units
mentioned above. The higher 'dpi' a printer has, the finer quality it
can print and the more lines per inch it can handle.
Typically this varies from 600dpi for an office laser printer to
3200dpi for a commercial printing workflow.
Using the Units Appropriately
When we scan a print, we use 'spi' (or 'ppi')
When we open a digital image in Photoshop, we use 'ppi' as a
guide of how it might output
When we view a digital image on a monitor, we use 'ppi',
although the overall pixel dimension will be of far more use
When we print out an image we need to know the printing
resolution of the output device, that is measured in 'lpi'
When we compare the quality or sharpness of a printer we use
'dpi'
File Formats
Choose a non-proprietary open 'standard'
Despite the large range of available file formats, choosing one
should not be too hard as only a very few of them are normally
recommended for digitisation projects. Any digitisation project will
need to consider the long-term usefulness and accessibility of the
images and this means choosing a file that is both an established
industry 'standard' as well as a non-proprietary format. This limits
the range to a much more easily considered number that includes
the most common four below:
TIFF (Tagged Image File Format)
PNG (Portable Network Graphics)
JPEG or JFIF (Joint Photographic Experts Group File
Interchange Format)
GIF (Graphic Interchange Format)
Page 4
File formats for desktop printing
The normal desktop printers (ink-jet and colour photocopier) are
designed to work happily with a range of image file formats,
including JPEG compressed files. However they will still work
best with the maximum amount of image data supplied by an
uncompressed image such as a TIFF or PSD.
File formats for web delivery
For most digitisation projects, the most common delivery format
is simply a monitor with the images viewed through a web
browser interface. This makes the choice of file format easy as
the current selection of web browsers only support a small range
of image file formats (JPEG, GIF & PNG), although this range can
be extended with the use of the appropriate plug-in.
The largest limitation on the quality of images delivered on the
web and the main influence on 'choice', is the need for them to be
compressed to a size that makes their delivery over the limited
available bandwidth possible. All the file formats supported by
web browsers provide compression, however the amount and
method of compression varies.
Web browsers currently support the following file formats:
JPEG (JFIF) - It is a lossy compression and will provide the best
quality and lowest file size for continuous tone images. The
amount of compression given to the file is chosen at the time of
saving the file and allows for variation in quality against file size:
as a rule of thumb, it is normally considered that a file
compressed with JPEG to 10% of its original size will be visually
acceptable with no obvious compression artefacts. However it is
common if required, to compress right down to 2-4% if the lower
quality is acceptable.
GIF - The Graphic Interchange Format, is an 8-bit (and under)
indexed file type only offering a range of 256 (or less) different
colours (these can either be a standard selection or a imagedependent selection by user-choice) and works best for use with
simple images using block colours, such as graphics, logos and
banners. The GIF file format supports layers allowing it to offer
both transparency and animation.
PNG - The Portable Network Graphics (colloquially called 'PING')
file is an open source 'standard' that was introduced to overcome
the possible patent problems associated with the GIF format.
However it cannot compete with the JPEG in terms of producing
high quality and small, full colour images for viewing on the web.
The compression available from PNG in 24-bit mode is typical for
a lossless compression providing a file of about 60-75% of the
original size and in 8-bit mode it is much the same as GIF. PNG
supports transparency (even variable opacity) but is not able to
provide animation.
Page 5
Need or Use
Recommended
File Type
Reason
Normal continuous-tone
full colour image at the
highest quality
JPEG or PNG
PNG will allow you to deliver an image at the highest quality using lossless
compression. However file size will be very large (approx 60% of original). JPEG at
its best quality setting, should be visually identical but provide a larger
compression (approx 10-25% or original).
Normal continuous-tone
full colour image at
highest compression
JPEG
JPEG will allow compression of the image down to approx 2-4% of the original
size. At this compression, quality is likely to suffer, but in some cases this can be
acceptable
A web banner or logo
with 8-bit or less colour
PNG or GIF
Both PNG and GIF offer the best compression for file size. PNG is 'patent' free,
but might have problems with older browsers
Continuous-tone
greyscale image
JPEG, PNG orGIF As greyscale is only 8-bit anyway, all of the formats should provide comparable
quality, however JPEG is likely to provide highest compression (with
corresponding drop in quality)
Black and White bi-tonal
images
PNG or GIF
In this case, GIF or PNG should provide equal quality. JPEG is not recommended
as it will give a file size larger thanPNG/GIF due to it being unable to store less
than 8-bit greyscale
Image or logo with
transparent layers
PNG or GIF
Both PNG and GIF support transparency.PNG is non-patented. PNG also offers
multi-layers and variable-transparency. Note this is not supported in older
browsers
A full colour image with
lossless compression
PNG
As stated above, only PNG allows you to deliver a losslessly compressed image
Animated image
GIF
At present only GIF can support animation
A zoomable or
streamable image
JPEG, JP2, VFZ
This will largely depend upon server software, however it is hoped that browsers
will be able to provide this with newer file types such as JPEG 2000 orVFZ
A file with reliable image
metadata tagging
JPEG, PNG, JP2
At present this is not supported by the current web browsers,
however JPEG andPNG both do support IPTC data. JPEG2000 also has an XMLbased inbuilt metadata system, which should hopefully be readable by future
web browsers
A file with integral rights
management
VFZ, JP2
So far all these systems will need some server-side software and plug-ins within
the user's browser, however again it is hoped that JPEG 2000 and next
generation browsers will be able to provide this functionality
Starting Photoshop
Depending on how Photoshop has been installed, we can either
start the program from an icon on the desktop, or by going
through the start menu. A desktop icon is normally created when
the program was installed unless this option was deselected.
How to start Photoshop
Double click the Photoshop icon.
Or, Start button...Programs...ITS Applications...Adobe Photoshop
CS5...Adobe Photoshop CS5
Click on the ‘Close’ button to remove the Welcome screen.
Page 6
The Screen
Before we look at the individual components, we shall familiarise
ourselves with the layout of the screen in Photoshop CS5.
Menu Bar
Tools Palette
Workspace View
Options Bar
Panels
Opening an image
Opening an image in Photoshop is very similar to opening a file in
any other program. Use the File menu, then Open, and then
browse for where the image is stored on your PC to open it.
Creating a new image
In Photoshop, you can create a new image from scratch, or use
an existing image, or part of one, as the basis for a new image.
To create a new image
Click File, then New
Make necessary adjustments via the dialogue box
Click OK
The New Image dialogue box
When creating a new image, you are given several options to
choose from including image size and resolution.
Page 7
Use the drop down arrows to change the unit types (e.g.
inches/centimetres/pixels), and click into the other boxes to
directly alter those figures. If you prefer, Photoshop has some
built-in preset sizes for ease of use. To access these, firstly use
the Preset drop-down to select a category, such as Photo, then
from the Size drop-down select your exact specifications, for
example: Landscape, 4x6 (Standard Photo Size).
The Tools Palette
Whatever action you wish to perform on your image you will firstly
need to select the appropriate tool from the Tools Palette. We
shall look at the actual tools more closely throughout the course
but for now we shall see what sort of things we can do and how
to access these tools.
The default tool is activated by simply clicking onto the icon to
select it.
Marquee Selection
Lasso
Crop
Pick
Quick Selection
Eyedropper
Spot Healing
Brush
Clone Stamp
History Brush
Eraser
Gradient
Blur
Dodge
Pen
Type
Path Selection
3D Object Rotate
Hand
Rectangle Shape
3D Rotate Camera
Zoom
Colour Picker
Extended Tools
Photoshop CS5 has a number of extended ‘hidden’ tools. These
are accessed by ‘flyout’ menus from the main tool palette. Most
(but not all) tools have extended options. If a particular tool has
more options available it will be displaying a small shaded
triangle at the bottom right corner of its icon.
Page 8
Accessing the extended tools
Right-click on the shaded triangle below the icon of the tool that
you wish to use
Highlight and click with the left button to select the tool
This option will remain selected until either an alternative is
selected, or when Photoshop is shutdown. When Photoshop is
restarted, the default tool option will once again be visible on the
palette.
The Options Bar
The Options Bar sits below the Menu Bar. This bar is contextual,
meaning it will differ depending on which tool you are using. The
options available will be to fine tune the tool that you are currently
using.
The Marquee tool Option Bar
Panels and Workspace
When you first open Photoshop, there are a selection of panels
that appear on the right side of the screen. The panels that
appear are dependent upon which Workspace View that is active.
The default workspace view is Essentials, and the default panels
are Colour, Adjustments and Layers. If you wish to alter which
panels are displayed, use the Window menu and click to place a
check mark next to the panels that you wish to display.
To change the Workspace View, click directly on the view name
in the Menu Bar.
Zooming
We can make very subtle changes to an image by zooming in on
the part we need to change. There are a variety of methods we
can use.
How to zoom using the zoom tool
Click in the Tools Palette to select the zoom tool.
Click on an area in the image to zoom in
Page 9
How to zoom using the keyboard
Hold down the CTRL key and press the + key to zoom in, or
Hold down the CTRL key and press the – key to zoom out.
Selection tools
The selection tools are at the heart of Photoshop. Although
sometimes we can work with the whole image or a whole layer,
quite often we need to work with a particular selection. The
advantage is that changes are only made to the selected part of
the image, and not any other part, so a careful selection protects
the rest of our image from accidental editing.
Choosing the correct tool
There are a number of different selection tools. It’s worth
practising with the different tools because some are more
appropriate in some circumstances than others. There are a
number of selection tools, which can be put into four main
groups. These are:
Rectangle marquee, Ellipse marquee, Single Row marquee
and Single Column marquee
Magic Wand and Quick Selection tools
Lasso tool, Polygonal Lasso tool and Magnetic Lasso tool.
Pen tool and Freeform Pen tool.
How to select with the Rectangle or Ellipse Marquee
Select the tool required from the toolbox
Click on the image at one corner of the area we want to select.
Hold the mouse button down and drag diagonally to the opposite
corner.
Release the mouse button.
Page 10
But I wanted a square or circle
We can force the selection to be a perfect square or circle by constraining
the selection as we make it. Constraining selections is explained on page 14.
How to select with the Single Row or Single Column
tool
Select the tool required from the toolbox.
Click on the image.
A selection one pixel tall and the same width as the image will be
made if the single row tool is selected.
A selection one pixel wide and the same height as the image will
be made if the single column tool is selected.
Zoom in
Because the single row and column tools make a selection with a dimension
of only one pixel it’s normally better to zoom in to make sure we’re selecting
the right row or column.
Quick Selection Tool
This tool allows you to ‘paint’ a selection of your image.
Dependant on the size of the brush tip, you can click and drag to
select a defined area of an image. This tool works particularly
well with images that have highly defined areas.
How to use the Quick Selection Tool
Click on the Quick Selection icon
Choose a start point in the image and click and hold the left
mouse button and drag to select the desired area
Magic Wand Tool
This tool is a little unusual since it makes its selection based on
colour. When we click on a particular pixel in the image, called
the seed pixel, the tool will look at the adjacent pixels. If the
adjacent pixels are a similar colour (and we can control how
similar by setting the tolerance) then these pixels are selected as
well. The tool then repeats the process until no more pixels can
be selected. The selection ‘grows out’ from the initial point.
But I wanted all the pixels of that colour
Other pixels of the same colour won’t be selected because the selection
grows outwards from the seed pixel. We can work around this problem and
pick every pixel within the tolerance by removing the tick from ‘Contiguous’ in
the toolbar.
How to use the Magic Wand tool
Click on the Magic Wand icon.
Click in the image on a particular seed pixel.
The options for this tool are anti-aliasing, contiguous, use all
layers, and tolerance.
Contiguous, as we have seen, controls whether we grow out from
our seed pixel or select everything of that colour in the image.
Page 11
Anti-aliasing smooths the transition between a selection and its
background.
Tolerance controls how close the other pixels in the image have
to be to the seed pixel before they are selected. Setting a larger
tolerance means that more pixels will be selected.
Use All Layers will control whether the Magic Wand will pick
pixels from the active layer or all layers in the image.
The Lasso Tools
How to use the Lasso tool
Click on the Lasso icon
Click and drag on the image. Release the mouse button.
Closing the loop
When we’re using the lasso tool we don’t need to close the loop. If we
release the mouse button and the loop isn’t closed then Photoshop will close
if for us using a straight line.
How to use the Polygonal Lasso tool
Pick the tool from the toolbox.
Click on the starting point of the area we want to select.
Click on another point of the area to be selected and it will be
joined to the first by a straight line.
Repeat until the area has been selected.
Move the mouse pointer over the first point. A small circle
appears next to the mouse pointer. Click to close the selection
outline.
Switching tools
If part of our area to be selected is curved then it can be quite laborious to
pick many points with the polygonal lasso tool. We can temporarily switch
back to the normal lasso tool by holding down the ALT key, dragging the
mouse pointer, and then releasing the ALT key to return to the Polygonal
tool.
How to use the Magnetic Lasso tool
Pick the tool from the toolbox.
Click on an edge of the area to be selected.
Move the mouse pointer around the area to be picked without
holding down the mouse button.
Click on the starting point to close the selection outline.
There are three options we can set to modify the tool. These are
width, edge contrast and frequency.
The width setting can vary between 1 and 256 pixels and sets
how close to an edge the mouse point has to be for Photoshop to
see the border. If the image has less contrast or the area has lots
of nooks and crannies in its border, then we can set it to a lower
setting.
Page 12
The edge contrast setting controls how much contrast there
needs to be between the area to be selected and the background
for the lasso to recognise the edge. The setting can vary between
1% and 100%. If there is a lot of contrast in the image then a
higher value will work better. If there is less contrast in the image
then choosing a lower value will be more successful.
The frequency setting controls how often the magnetic lasso will
insert its anchor points. The setting varies between 1% and
100%.
Feather and Anti-Alias
We can use feathering and anti-aliasing with any of the four tools,
with the exception of Rectangle Marquee, which only has the
feathering option.
Feathering
Feathering allows us to have a smoother transition between our
selection and the background. We can choose the radius (how
many pixels) to feather by. The following images show the effect.
(A)
(B)
Image (A) with AntiAliasing On and (B)
with the setting Off.
Note the jagged edge
of Image (B)
(A)
(B)
Image (A) with
Feathering set to 0
pixels and (B) with it
set to 20 pixels. Note
the smoother border
of Image (B)
It didn’t work
For feathering to work, we have to select the option before we make the
selection. Turning on feathering after the selection is made will have no
effect.
Page 13
Anti-aliasing
Our image is made up of little squares, the pixels. If we select
diagonally some of the pixels will be selected and some won’t.
This results in the ‘smooth’ edge of our selection looking like a
staircase. With anti-aliasing switched on then the software puts
intermediate colours into some of the squares, which has the
effect of smoothing out the transition.
Constraining selections
By constraining selections, we mean forcing them to be perfect
squares or perfect circles, which are particularly difficult tasks to
do by eye because the individual pixels are so small. We can
also constrain selections to that they are centred on the point we
select rather than start from that point.
How to make a perfectly square or circular selection
Select the Rectangle or Ellipse Marquee tools.
Click and hold down the mouse button and drag to select
Hold down the SHIFT key after starting to make the selection.
Release the SHIFT key.
How to centre a selection
Select the Rectangle or Ellipse Marquee tools.
Click and hold down the mouse button and start to drag to make
a selection.
Hold down the ALT key after starting to make the selection.
Release the ALT key.
But I wanted a perfect square centred
We can make a square or circular selection centred on a point by holding
down both the CTRL and SHIFT keys while dragging to create the selection.
Modifying selections
It’s rare than we can make the selection that we want in one step.
We might need to remove part of the selection or add another
part to it, or even to select the area that intersects two selections.
We can modify our selection either by using the keyboard or by
using the buttons on the options toolbar.
The four buttons are, from left to right, make a new selection, add
to the existing selection, delete from the existing selection,
intersect the two selections.
Page 14
How to add to a selection
Click the ‘Add to Selection’ button on the options toolbar, or hold
down the SHIFT key before starting to make the selection.
Click and drag to make the selection.
How to remove part of a selection
Click the ‘Subtract from Selection’ button on the options toolbar,
or hold down the ALT key before starting to make the selection.
How to choose the intersection of two selections
Click the ‘Intersect with Selection’ button on the options toolbar,
or hold down the Alt and Shift keys before starting to make the
selection.
What does the shift key do?
We can use the SHIFT key either to force a selection to be a perfect square
(or circle) or to add to the selection. So how does one key do two jobs? It
depends on when we press the key down. If we press and hold it down
before making the selection we will add to the selection. If we press and hold
the key down after starting to make the selection then we will constrain the
selection to a perfect square or circle.
Viewing multiple images
There may be occasions where you are working on several
images at the same time. In order to be able to move from image
to image you need to know how to switch between them.
How to switch between images
Use the tab bar directly above the image, or:
Click the Window menu. At the bottom of the menu will be a list
showing all currently open images. Click the one you wish to
view.
Copying and Moving
A very common task with a selection is to copy or move it,
perhaps even to a different image to create a composite image.
We can choose to copy or move either by using the keyboard or
by using the icons and menus.
How to move a selection using the mouse
Select the area of the image to be moved.
Click on the Move Tool.
Move the mouse pointer inside the selected area.
Click and drag to move the selection to its new location.
Page 15
How to move a selection using the keyboard
Select the area of the image to be moved.
Press CTRL-X. This will cut the selection.
Go to the destination for the selection, for example a new or
different image or a different layer in the current image and either
Press and hold down the CTRL key and press and release the V
key, or click on the ‘Edit’ menu and click on ‘Paste’.
How to copy a selection
Select an area of the image.
Press CTRL-C, or click on the ‘Edit’ menu and click on ‘Copy’.
Go to the destination for the selection, for example a new or
different image or a different layer in the current image and either
Press and hold down the CTRL key and press and release the V
key, or click on the ‘Edit’ menu and click on ‘Paste’
Transforming a Selection
When we select part of an image for use elsewhere, we may wish
to transform it in some manner. This could involve stretching,
resizing, or rotating the selection.
Applying a transformation to a selection
Firstly make the selection using one of the methods described
above
Click Edit...Transform...and then choose the transformation type,
or...
Click Edit...Free Transform...to apply a quick stretch or resize
Apply the transformation by clicking and dragging the handles
around the edge of the selection
From the Options Bar, click Commit Transform to apply the
transformation, or Cancel to try again
Where is it pasted?
If we paste into our original image without choosing our destination, then our
selection will be pasted into a new layer immediately above the original
layer. This will happen regardless of whether we are moving or copying.
Page 16
Cropping an image
Sometimes we need to only use part of an image. We can crop
the image by selecting a rectangular area that will effectively
become the image; the other parts of the image will be lost.
Selected area
highlighted and
ready to crop from
the full image.
How to crop an image
Click on the crop tool.
Click and drag on the image to mark out a rectangular area with
handles.
Press ENTER, or click Commit to crop the image, or ESCAPE to
abandon the crop.
Correcting editing mistakes
Sometimes, we may not be sure of what steps we need to take to
get the required end result. We might apply a filter, or adjust the
curves or levels and simply not be happy with the end result.
Luckily, our editing actions are reversible by using the undo
feature.
You may be familiar with the undo and redo features from other
programs such as Word or Excel. Photoshop does have a menu
item called Undo, but it also has two others: Step Forward and
Step Backward. Think of the editing actions that we do as a list of
instructions. If we choose to Step Backward we go back one step
in the list of instructions. Once we’ve stepped backwards we can
Step Forwards to come forward again in the list.
Page 17
How to Step Forwards or Step Backwards
Click on the Edit menu.
Click on Step Backwards to go back one step in the editing
history, or
Click on Step Forwards to go forward one step in the editing
history.
It can sometimes be difficult to tell what the next step to be
undone (or redone) is. We also have a visual representation of
the editing history and we can undo a series of editing actions to
return to a previous ‘image state’ by clicking in the list.
How to use the History panel
Click the History button (alongside the Navigation panels)
Select the image state that you wish to go to
Either choose to take a snapshot of the image at the selected
state, or delete the state
Page 18
Layers
Using layers is one of the most fundamental skills for working
with digital images, but also one of the most unfamiliar. We tend
to think of an image as a single entity, like a piece of paper onto
which we can draw or paint, but that isn’t necessarily the case.
Before computers, cartoons were hand painted onto transparent
sheets called cels. There would be a background, then a cel for
Snow White, another cel for Grumpy, and so on. The cels would
be placed one on top of each other and then photographed to get
an image. For the next frame, the cels would show the characters
in slightly different positions. By using this technique, one team of
artists could work on all the cels for a particular character and
another team of artists would work on the cels for another
character.
We use layers in Photoshop for the same reasons. With a
particular part of an image on a particular layer, we can work with
that area in isolation without affecting the other areas of the
image. We can also achieve some creative effects by controlling
the blending between the layers.
Layers will be expanded upon in the Advanced course, but for
now we shall get to grips with the basics.
(A)
(B)
(C)
Original Images
(A) and (B)
combined as
separate layers to
create Image (C)
Page 19
The Layers Palette
How to display the Layers palette
Click on the ‘Window’ menu and click on ‘Layers’, or
press the F7 key.
How to select a layer
Either click on the layer thumbnail in the layers
palette or click on the layer name.
How to make a layer visible
Click to the left of the layer thumbnail. An eye
symbol is present when the layer is visible.
My image isn’t changing
When we edit, we make changes to the active layer, but a layer can be
active without being visible. This can cause problems because we’re trying
to edit and think nothing is happening, but we are actually making changes
to our image that we can’t see.
Editing layers
There are a variety of editing processes that we can do with
layers. Copying a layer is particularly useful, because it leaves an
original copy intact. We can then try something and either delete
the original (if we succeeded) or delete the new copy (if the
editing didn’t work).
How to add a new layer
Click on the New Layer icon, or
Click on the Layer menu, move over New and click on Layer.
How to copy a layer
Click on the Layer menu, move over New and click on Layer Via
Copy.
How to delete a layer
Select the layer and click on the Delete Layer icon.
When there is an image with a number of layers, we often have
to move them up or down in the stacking order so that we can get
the end result that we want.
How to move a layer up or down
Click on the layer name to make the layer the active layer.
Click and drag the layer up or down within the layer palette to the
required position.
Some file formats don’t support layers, so we will need to ‘flatten’
the image before we save it. Alternatively, we might want to
combine a number of layers we’ve worked on into a single
component. We can choose to merge particular layers, merge all
layers, or flatten the image.
Page 20
How to merge two layers
Select the top layer of the two.
Click on the ‘Layer’ menu and click on ‘Merge Down’,
Or right-click on the layer name and click on ‘Merge Down’.
How to merge all visible layers
Click on the ‘Layer’ Menu and click on ‘Merge Visible’,
Or right-click on the ‘Layer’ name and click on ‘Merge Visible’.
How to flatten an image
Make all the layers to be merged visible.
Click on the ‘Layer’ menu and click on ‘Flatten Image’.
Or right-click on the ‘Layer’ name and click on ‘Flatten Image’.
Flattening vs merging all visible
Flattening an image is not the same as merging all visible layers. If we have
five layers, three of which are visible, then merging all visible will result in the
original two non-visible and the new merged layer. If we flatten the image,
then the two non-visible will be deleted and the merged layer will be the only
layer left.
How to rename a layer
Double-click the layer name in the Layer palette.
Type the new name and press ENTER.
Layer Blending Modes
There are a number of different ways that we can blend a layer
with the one below it. The most basic thing we can do is to vary
the opacity (transparency) of the layer, so that the layer beneath
shows through.
How to vary the opacity
Click on the arrow to the right of the opacity setting.
Click and drag the slider to a new position.
Covering the other blending modes in detail is beyond this
introductory course, but they fall into a number of groups, and
you may want to experiment with them to see their effects. They
fall under the general categories of darkening, lightening,
inverting, and enhancing the saturation and brightness of the
image.
Page 21
Correcting and Enhancing Photographs
We might find that the photograph has a colour cast, where there
is more of one colour than there should be, or the image might be
over- or under-exposed, or it might be that the image looks
washed out. These are all problems that we can correct in
Photoshop. We can also use some of Photoshop’s tools to
enhance an image and give it a totally different look.
Brightness/Contrast
A common issue when using particular images is that they may
appear either too dark or too bright. This could be the result of
under or over using the flash or it may just be the weather
conditions on the day.
(A)
(B)
Original
image (A)
taken on a
dull day.
Image (B)
after
increasing the
Brightness.
How to adjust the Brightness or Contrast
Click on the Image menu, then Adjustments...Brightness/Contrast
Use the sliders to increase or decrease the levels
Click OK
Watch whilst you work
When using most of the correction and adjustment tools in Photoshop, there
will be a Preview option available. Leaving this checked will allow you to see
the adjustments as you make them so you will only need to confirm the
changes when you are sure that the image looks exactly as you’d like it.
Page 22
Colour Levels and Colour Curves
The Levels and Curves options can be quite technical and
generally go beyond the scope of this introductory course.
However, we shall take a brief look at the potential of these tools
and what they are used for.
One of the uses of this tool would be if an image appeared to be
‘heavy’ on one particular colour. For example, we may take a
photograph that has a large area of the sky in the background.
This could potentially make the whole image appear with a tint of
blue. Using the colour levels or curves we could attempt to
reduce the amount of blue in the image, thus giving it a more
balanced look.
How to use the Colour Levels and Curves tools
Click the Image menu, then Adjustments, then either Levels or
Curves
From the Channel menu, choose either to adjust all colours
(RGB), or to isolate a particular colour
Use the sliders, or click directly in the number boxes to adjust the
Input and Output levels
As mentioned, these tools can be quite technical to use correctly, however
by simply concentrating on the Input/Output levels you can achieve a
relatively good result. As a rule of thumb – reducing the Output levels will
lessen the amount of that colour in the image and increasing it will add to it.
A
B
C
In this example, we
have chosen to
isolate the Green
channel (A), and then
by dragging upwards
on the Curve line (B),
we have slightly
increased the
Output of Green that
will appear in the
image (C).
Page 23
Photo Filter
Using photo filters is an easy, straight-forward way of changing
the ‘mood’ of a particular image.
Applying a Photo Filter
Click the Image menu, Adjustments, then Photo Filter
Select a particular Filter from the drop-down menu
Alter the colour or density of the filter, if necessary
Click OK
Original Image (A).
With a Warming Filter
applied (B), and also
with a Cooling Filter
applied (C).
A
B
C
Using Black & White
Changing a colour image into Black & White can give it a more
‘classic look’ and can be applied very quickly and easily.
Changing an image into Black & White
Click the Image menu, then Adjustments, then Black & White
Click OK
A
B
Original colour image (A) and then with a
Black & White adjustment (B)
Page 24
Red Eye Removal
A common problem when taking photographs is that some times
the flash can produce ‘red eye’. Fortunately, Photoshop has an
in-built tool that allows us to eliminate this problem very easily.
Using the Red Eye Tool
Select the Red Eye Tool from the Tools Palette
n.b. The Red Eye Tool is an Extended Option of the Spot Healing Brush
Change the Amend and Darken amounts from the Options Bar as
appropriate
Click and hold the left mouse button and ‘brush’ over the eye(s) in
the image
Repeat the process until all red has gone
A
B
Original Image (A) and after using the Red Eye Tool (B)
Blur
The Blur Tool can be very useful in a number of situations. For
example, you may have pasted several objects to create a
layered image and you could use the Blur Tool to soften the
edges of the objects, or you could use it to make a particular part
of the image stand out by blurring the background. Alternatively,
you can use the tool to blur the faces of people in your images
that may need to stay anonymous.
Using the Blur Tool
Select the Blur Tool from the Tools Palette
Adjust the Brush Size and Type from the Options Bar
Click and hold the left mouse button and ‘brush’ over the image to
blur the selected area
Blurring the
background of the
image to make the
person in the
forefront stand out
Page 25
Filter Gallery
Using Filters is a quick and easy way to completely transform
your image into something totally different.
If you know the Filter that you wish to use you can pick it straight
from the list. However, if you wish to try out the various ones
then use the Filter Gallery.
Applying a Filter from the Filter Gallery
Select the Filter menu, then Filter Gallery
A new window will open with 3 panels – the 1st will show the
image, the 2nd will be the different categories of Filters and the 3rd
will be where you can fine tune a particular filter
Select a category to view the different filters
Click on the thumbnails to temporarily apply a specific filter
When you have chosen a filter, fine tune the settings in the 3rd
panel
Click OK to confirm
A
B
C
Original image (A) followed by Glowing Edges Filter (B) and Note
Paper Filter (C)
Page 26
The Type Tool
The Type Tool is required when you wish to add any extra text to
an image. There are a number of fonts and formatting options
that you can use when using the Type Tool.
Using the Text Tool
Select the Type Tool from the Tools Palette
Click onto the image to add a typing cursor
Enter the text as required, and amend any necessary options
from the Character Panel
Click Confirm to accept
Character Options
A
B
C
D
E
Use the drop-down menus
to change various options,
such as:
A.
B.
C.
D.
E.
Font Name
Font Type
Font Size
Font Colour
Font Styles
Added text to an image
Page 27
Images for the Web
When we display images on the web, we want them to be
displayed accurately and download quickly. To do this we need to
produce an image at the final size it will be displayed at and using
the correct resolution for the screen.
For example, a digital camera might produce an image of 2048
pixels high and 1536 pixels wide, with a file size of perhaps 2MB.
A typical screen size might be 1024 x 768 pixels, so only a
quarter of the image would be seen. The html code could be
changed to make the image say, 300 x 200 on the screen, but all
we're doing then is cramming the same picture information into a
smaller area. Plus we still have to download a 2MB file, and on a
dialup connection that would take about seven minutes for that
single picture alone.
The resolution will depend on what the output media will be. For
print, images might be prepared at 300 dots (or pixels) per inch,
or more for professional work. For screen display, the resolution
is 72dpi.
To optimise an image for the web we would:
Crop the image if possible to show a smaller area of interest.
Resize the picture to the final size to be used for the web page.
Reduce the resolution of the image.
Save the image in its output format.
Work on a copy
It’s a very good idea to do this work on a copy of the image, so that we
always have the original. That way, we could produce a thumbnail image
and a full size image for a web page, and a higher resolution image for print
work, all from the same original source file.
A
Showing
various file
formats and
sizes (A). Use
the Preview
button (B) to
see how it
looks displayed
in a browser.
B
Page 28
How to change size and resolution of an image
Click on the ‘Image’ menu and click on ‘Image size …’, or press
CTRL-ALT-I.
Set the resolution under the ‘Document Size’ section.
For a web image, set the size in pixels in the ‘Pixel Dimensions’
section.
For a print image, set the image dimensions under the ‘Document
Size’ section.
Click on ‘OK’.
Page 29
Appendices
Full List of tools available from Tools Palette
University Communications Guidelines
Available on the staff intranet for employees only. A guide for
using the University brand and logos on a variety of publications.
https://www.intranet.bham.ac.uk/onlinecomms/brand/index.shtml
Page 30

Digital images CS5 (PDF - 2.2MB) - University of Birmingham Intranet

Transcription

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