Magnetic Lasso Tool

The Magnetic Lasso Tool is a smart selection tool that automatically detects and snaps to the edges of objects as you move your cursor along them. It analyzes color and contrast differences to place anchor points along the boundary between the subject and its background.

This tool is incredibly useful for selecting objects with well-defined edges against contrasting backgrounds, such as a person standing against a clear sky or a product on a white surface. It strikes an excellent balance between automation and manual control.

Where to Find It

It is the third tool in the Lasso group. Click and hold the Lasso icon, then select the Magnetic Lasso Tool from the flyout menu. Press L then Shift+L twice to cycle to it.

How to Use

• Click to start: Click on the edge of the object you want to select to place the first fastening point.
• Trace the edge: Move the cursor (without pressing any mouse button) along the edge of the object. The tool automatically places anchor points along high-contrast edges.
• Add manual points: If the tool goes off-track, click manually to add a forced anchor point and guide it back to the correct edge.
• Remove wayward points: Press Delete or Backspace to remove the most recently placed anchor point.
• Close the selection: Hover over the starting point and click when the circle icon appears, or double-click anywhere to close with a straight line.

Settings & Options

• Width: Defines how close to the edge the cursor must be for detection (1–256 pixels). Lower values for detailed, high-contrast edges.
• Contrast: Sets the sensitivity for edge detection (1%–100%). Higher values detect only strong contrasts; lower values detect subtle changes.
• Frequency: Controls how often anchor points are placed (0–100). Higher values place more points for complex, winding edges.
• Pen Pressure: If using a graphics tablet, enables pen pressure to control Width dynamically.

Pro Tips

• For low-contrast edges, lower the Contrast value and increase the Frequency to help the tool stay on track with more manual guidance.
• Work at high zoom levels (200%+) and adjust the Width to a smaller value when selecting intricate details like hair or fur.
• After completing the selection, use Select & Mask to refine tricky edges, especially around fine details that the Magnetic Lasso may have missed.

Common Mistakes

• Using it on low-contrast images: The Magnetic Lasso struggles when the subject and background have similar colors or tones. In such cases, use the Pen Tool or a channel-based selection instead.
• Moving the cursor too quickly: Moving too fast causes the tool to miss edges or place anchor points in the wrong locations. A steady, moderate speed gives the best results.