The Lasso Tools

The selection tools you will likely use most often are the Lasso tools (normal, polygonal and magnetic lasso). You choose the one you want by clicking the little arrow at the bottom of the Lasso tool selector (keyboard shortcut - L).

At the top of the screen are the modifiers for the three primary selection tools. With each one of these options you can change how the Lasso tools behave.

The first box on the left of the modifier bar is the lasso tool currently selected - the magnetic lasso tool in this illustration.

To the right of the selected lasso tool are four little icons. From left to right they are: Normal Selection; Add to Selection (Keyboard Shortcut - press and hold the Shift Key); Remove from Selection (Keyboard Shortcut - press and hold the Alt/Option key); and, Intersection of two Selections.

The next two to the right are Feathering, and Anti Aliasing.

Anti-aliasing smooths the jagged edge of a selection by softening the edge transition between edge pixels and background pixels. Since only the edge pixels change, no detail is lost. It is useful when cutting, copying and pasting selections.

You must choose anti-aliasing before using any tools.

Feathering blurs edges by building a transition boundary between the selection and its surrounding pixels. This blurring can cause some loss of detail at the edge of the selection.

You can change the amount of feathering at any time.

To the right of Feathering and Anti-Aliasing are three more options - Width, Edge Contrast and Frequency.

To understand how these additional 4 options improve your selections you need to know one more thing ...

If you press the CAPS LOCK key with the Magnetic Lasso Tool selected you will see the familiar selection cursor change to a circle with a crosshair in the middle.

To select an object, place the crosshair on the edge you would like to select and right click (or tap your pen) once, let go and float your cursor around the object. The magnetic lasso constantly searches within the circle to find an edge to cling to which means you need to keep the edge within the circle.

Width determines the size of the circle ...

Edge Contrast determines how much contrast there must be between the background and the object you are selecting. The higher the setting the more contrast there must be for a good cling ...

Frequency determines how many points will be laid down, and ...

Pen Pressure controls the width - as you press harder with the pen the selection area becomes smaller and smaller and produces very precise selections.

With a pen tablet, then, you can be very precise in your selections because as you press harder the width becomes smaller.

An Example

This is the original picture of Anna, the Bull Terrier. She is such a sweetie and loves having her picture taken!

This is the selection I did with the mouse and Caps Lock on. For some reason the magnetic lasso found something of interest on Anna's back, her head and her nose so it wandered in there to have a peek.

I could have fixed this selection by clicking the add to selection check box - but there is a better way to do the selection.

The easier and much more accurate way is to use a pressure sensitive pen with CAPS LOCK pressed and pressure sensitivity selected. It is easy to see how much more accurate the selection is with the Graphire pen than it is with the mouse.

The selection took about the same amount of time but there is no need for any additional work with the pressure sensitive pen and tablet.

Go ahead and play with this. Even if you do not have a graphics tablet (yet), you will find your mouse selections so much better. When you add in the tablet your selections will be much more accurate the very first time you try it out!


Return to Photoshop Tutorials from Lasso Tools.