One of the primary skills of image manipulation is not only learning how to make a selection but also learning how to make the best selection possible.
"What is a selection and why is it an important
skill?"
A selection is an area of a digital image bounded by what is quirkily named
as 'marching ants' - a moving dotted line. All the pixels within the selection
area can be worked upon and manipulated in isolation to the unselected parts
of the same image.
A selection is important for many reasons for example like cropping, moving bits of one image onto another image, improving shadow detail without affecting the overall light balance of other areas of a photograph, changing the colour of a person's eyes to reduce red-eye, etc. Well in fact the list is limitless and knowing how to make a good selection based upon the number of tools available to the digital artist is crucial in becoming more professional in your digital manipulation. This tutorial will focus mainly on Photoshop but much of the techniques can be applied to other packages although obviously the shortcut keys won't be the same.
Basic Tools
There are several methods of creating a selection in Photoshop from the basic
Marquee tools (quickly accessed by pressing M on the keyboard), which gives
you the option of creating a Rectangular or Elliptical Marquee.
(Tip - Pressing the Shift key when dragging out
a marquee will give it a Fixed Aspect Ratio to ensure a true square Rectangle
or a true circle Ellipse)
These basic marquees are very useful at making quick selections and when combined
with Select>Transform Selection can be manipulated into a great variety
of shapes to suit your selection. There are two other marquees the Single
Column and the Single Row marquee which can be used in pixel art to create
straight lines when you apply a fill to the selection.
More advanced tools for selection come in the form of the Lasso Tools (Quickly accessed by pressing L on the keyboard)
The Lasso
The Freehand Lasso - just referred to, as Lasso Tool in Photoshop - will let
you make a freehand selection with the mouse or a graphic tablet pen, this
is extremely useful for making very difficult selections that more require
the human eye than complex computer algorithms to determine a selection edge.
This tool is probably one of the hardest to master, as it requires a steady
hand, but zoom in on the detail of the image to ensure that any unsteadiness
isn't so noticeable.
The 'freehand' Lasso Tool
Polygonal Lasso
The next Lasso Tool is the Polygonal Lasso so named because it creates a polygon
shaped selection - a polygon being a multisided object - the Polygonal Lasso
creates a straight selection line between two points or mouse clicks this
way you can describe a shape by clicking around your intended selection area
until the points meet back at the start point
The Polygonal Lasso Tool
(Tip - if you experience problems finding the starting point simply double click the mouse or press the Enter key and it will close the polygonal selection for you).
Okay you may think that the Polygonal Lasso creates a very angular selection but what if the subject area is curved - well getting close up to your subject by zooming in will allow you to make more mouse clicks closer together therefore you can describe a pretty good curve with the Polygonal Lasso alone, however, the next Lasso tool is even more suited to making more professional selections.
Magnetic Lasso
The Magnetic Lasso Tool works by calculating contrasting pixels to determine
what is an edge and what isn't and 'magnetically' snaps an anchor point to
what it thinks is an edge.
The Magnetic Lasso Tool
Okay it seems an ideal tool for all jobs, but don't be so hasty, as with all the selection tools taking some time to know what each can do and more importantly what each can't do will pay off in multiples when you come to making more professional selections later on. The Magnetic Lasso can only make a guess based upon the information is can gather about the level of contrast within surrounding pixels, in a high contrast image the Magnetic Lasso will cope easily with it's default settings but with lower contrast images then you may need to adjust the Edge Contrast percentage of the tool, also try to help the lasso make the selection by clicking an anchor point in areas it cannot read so well - basically don't allow the Magnetic Lasso to dictate where it wants to place an anchor point but allow it to make the easy decisions and leave the real brain work to you, after all it's your selection and you must be happy with it.
Magic Wand
Another selection tool is the Magic Wand (W on the keyboard)
The Magic Wand Tool
This is a great tool if used properly but don't believe for a second that it can magically create the perfect selection, very little can be achieved in digital manipulation without fully understanding the tool you are using. The Magic Wand like the Magnetic Lasso works by determining edge contrast but instead of making a point-by-point selection it finds a block of similarly coloured pixels and makes a selection around them - all very easy and quick if you have solid blocks of colour like in a .png or.gif image but not so easy where there is a high level of colour blending like in a photograph. By setting the Tolerance setting higher on the Magic Wand tool it will include a wider range of similarly coloured pixels into the selection but then it will find it harder to determine a low contrast edge - so you need to play about with this tools and it may be frustrating at first but understand there is no magical solution to a good selection just having a keen eye and remember the only tool that can make the most perfect of selections is you, so don't rely too heavily upon quick-fix tools, get down and dirty at the pixel level by zooming right in, use the Hand tool (Space Bar) to navigate around the image, and take your time making a good selection - as the results of a good selection more than make up for the time it takes to make it, and with practice you will find that it will become second nature to get down to the pixel level.
Pen Tool
Finally the last tool in the selection arsenal is the Pen Tool (P on the keyboard
- no don't pee on the keyboard! - you know what I mean).
Beware the common mistake - when you come to use your pen tool for the first time you may start out drawing only to notice that the path begins to fill with the foreground colour this is because the Pen Tool not only is a Path tool but also shares the function of a Shape Layer tool
The Shape Layer tool
To ensure you are creating a vector path rather than a vector shape click the icon to it's right with the pen image - you will probably have to delete the first shape layer as well.
Most professionals use the Pen Tool more often than any other selection tool and in fact it's not really a selection tool at all but a Path Tool for creating vector paths but has the advantage of being able to create a selection from the path. The advantage of the Pen Tool is that in creating your path you can tweak the anchor points to your hearts content define the perfect selection long before you have to commit the path as a selection - and even if you do the path will still be there for you to tweak again and again until your satisfied with your selection.
The Pen Tool
The Pen Tool creates a vector path, which means it creates what is called Bezier anchor points that can be altered to create perfect curves or straight lines the path itself is stored in the Paths palette and when you require it to make a selection simply right click the path's icon and select 'Make Selection…' or click the 'load path as a selection' icon at the bottom of the palette.
When you right click the icon and select 'Make Selection…' it will bring up a dialogue box, which will offer you options like setting the Feather Radius value, an Anti-aliased checkbox and how you wish the selection to be applied; New Selection, Add to Selection, Subtract from Selection, Intersect with Selection.
As a default I prefer 0.5 pixels feather radius, and anti-aliased checked which gives a good selection with slight feathering to ensure a smoother selection - these setting work well for most masking or layer operations.
Working with more than one selection
Okay you have played around with the various selection tools but you find
that no one tool seems ideal to do the job, so how do you combine various
selections to get the one you want? There are a few keyboard commands that
you can use in combination with selection tools to add to, subtract from,
or intersect with an existing selection.
Adding to a Selection:
[Shift]
By pressing the Shift key you can drag out or draw another selection, which
will be added to any existing selections you have on screen.
(Once you have pressed the Shift key and started to drag out or draw your
selection you don't need to keep the key pressed and a + sign will appear
next to your cursor to indicate that it will add to your existing selection)
Subtracting from a Selection:
[Alt] Windows [Option] Mac
By pressing the Alt key (in Windows) Option key (on the Mac) you can drag
out of draw another selection that will be subtracted from the existing selection.
(Once you have pressed the Alt key and started to drag out or draw your selection
you don't need to keep the key pressed and a - sign will appear next to your
cursor to indicate that it will subtract from your existing selection)
Intersecting with a Selection:
[Shift-Alt] Windows [Shift-Option] Mac
By pressing the Alt key (Option key on the Mac) simultaneously with the Shift
key you can drag out draw a selection, which will intersect with the existing
selecting.
(As above you don't need to keep the keys pressed once you have started to
drag out draw your selection and an x sign will appear next to your cursor
to indicate that it will intersect with your existing selection)
Note - All the above options can be made using the Selection Palette by click on the appropriate icon
The Selection Palette
Making a Quick Selection:
If your image is already on a transparent background, or your image is masked
then you can make a quick and easy selection just by pressing and holding
the Ctrl key (Command key on the Mac) while you left mouse click on the either
the Layer Thumbnail or the Layer Mask Thumbnail in the Layer Palette. This
will create a selection based upon visible pixels leaving all hidden or transparent
pixels unselected.
Well I hope you found my tutorial on Selections useful - I will continue with
the tutorial to bring in Layers and Masking.
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