Last updated Tuesday, Oct 17, 2006

Photoshop 101 - The Lasso Tool

The Lasso Tool is another invaluable tool for making selections. For those with an unsteady hand or a hangover the Magnetic Lasso Tool will also save serious time in cutting out selections.

Estimated reading time: 3 minutes

Basics:

The Lasso tool is used for selections where there is no pre-defined shape. Unlike the Marquee Tool where you can select areas using circles and rectangles, the Lasso tool gives you more freedom in the shapes you select. To select the Lasso Tool click L. By default this will select the standard Lasso tool. To cycle through the Tools press Shift + L.

Standard Lasso Tool

The standard Lasso Tool allows you to select areas by freehand. Simply click and drag to select the outline of your area. To complete the selection drag the mouse back to the start point. At this point you will see the familiar black and white line of a selection. If you let go of your path half way through it will complete the path for you with a straight line back to the first click.

Freehand Selection with the Lasso Tool

Tip: To Create straight lines hold down the ALT key as you draw the path. What this does is to toggle between the standard tool and the Polygonal Tool.

Polygonal Lasso Tool

The Polygonal Lasso Tool allows you to create selections using straight edges. Each click you make will create a point until you return to your original starting point.

Refining your selection

The same selection tools that we saw in the Marquee Tool are available allowing you to add, subtract and intersect to your selection.

Magnetic Lasso Tool

If like me you haven’t got the steadiest hand you will love the Magnetic Lasso Tool. For images with a high contrast background this makes cutting out selections simple.

Making a selection with the Magnetic Lasso Tool

Click to start your selection and move your mouse. You will notice that the line will wrap to where it thinks the edge of the selection should be. Generally Photoshop does an amazing job but there are times when it will be wrong. To correct this by eye hit the delete button. This will remove the last way-point (the little square) and will allow you to try again. You can also click to define a way-point if you wish. To complete your selection return to the starting point. You will see the icon turns to show a little circle when you are over the start point.

Cutting out a shape using the magnetic lasso

Tip If you are not happy with your selection and want to start again hit escape. This will remove the path you have selected.

Magnetic Lasso Tool - Additional options

Width: This is the distance between the cursor and the edge of the selection that the tool can detect. This determines how precise you want to be when tracing. A small value makes the edge more precise. Most of the time a low value (e.g. 1px) is what you will need.
Frequency: This controls how often points are drawn by the Magnetic Lasso tool. Low values are good for smooth edges, high values are good for uneven edges.
Edge Contrast: This controls how much the contrast between pixels needs to be before the tool snaps to it. A high value is good when the background is in high contrast, a low value is good when the background is in poor contrast.

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