Adjusting the Magnetic Lasso Options in Photoshop

The Magnetic Lasso tool comes equipped with a few settings in the Options bar that control the sensitivity of the tool.

I recommend starting out by messing around with the Magnetic Lasso tool using its default settings. If the tool isn’t cooperating, then play with the options.

The first icon has to do with Tool Presets, and the next four icons are the selection state icons. The Feather and Anti-aliased options work like they do with the marquee tools (see the earlier section, “Using the marquee options”). The following list explains the remaining options:
-->Width: This option, measured in pixels from 1 to 256, determines how close to the edge you have to move your mouse before the Magnetic Lasso tool recognizes the object you’re selecting.
Decrease the value if
- The object’s edge has a lot of indentations and protrusions.
- The image is of lower contrast.
Increase the value if
- The image is of higher contrast.
- The image has smoother edges.
When using the Magnetic Lasso tool, you can change the Width value from the keyboard by pressing the open bracket ( [ ) key to lower the value and the close bracket ( ] ) key to increase the value.

-->Edge Contrast: Measured in percentages from 1 to 100, this option specifies the required contrast between the object you’re selecting and its background before the Magnetic Lasso tool hugs the edge between them. If your image has good contrast between the foreground and background, use a higher percentage.

-->Frequency: This setting, measured in percentages from 1 to 100, specifies how many points to place on the selection line. The higher the percentage, the greater number of points.
- If the object you want to select has a fairly smooth edge, keep the percentage low.
- If the edge is jagged or has a lot of detail, a higher percentage may be more effective in getting an accurate selection line.

-->Pen Pressure: If you own a pressure-sensitive drawing tablet, select this option to make an increase in stylus pressure cause the edge width to decrease.

Having it both ways with the lasso tools

Which tool do you use if you have an object with both curves and straight sides? You can have two, two, two tools in one! Press the Alt (Option on the Mac) key to have the Polygon Lasso tool temporarily transform into the regular Lasso tool. Then drag to select the curves. Release the Alt (Option) key to return to the Polygon Lasso tool. And this trick works with the regular Lasso tool as well. Press Alt (Option) to temporarily access the Polygon Lasso tool. When you want the regular Lasso tool back again, just drag your mouse. In this case, you can hold down the Alt (Option) key; it makes no difference. If you want to release the Alt (Option) key, just make sure that you’re pressing down the mouse button; otherwise, Photoshop will close the selection.

To temporarily change the Magnetic Lasso tool into the Polygon Lasso tool, press the Alt (Option on the Mac) key and click. As you hold down the Alt (Option) key, drag to get the regular Lasso tool. When you want the Magnetic Lasso tool back again, release the Alt (Option) key and move your mouse without clicking.