How to use the Lasso tools in Photoshop

Each photo editing program offers essentially the same basic functions at their core. The may have slightly different names, they may be found in different places, but their function is pretty much the same. This set of articles will describe the tools as laid out in Photoshop CS2, but the techniques, tips, and tricks in using them will be fairly transferable to different versions or different platforms.

This is the second in our series of articles describing the various editing tools available in Photoshop. This article will look at the lasso tools. As before, it is not the intention of our articles to suggest when you should use any specific tool, but merely to help you get comfortable with the various elements of each tool. There is always more than one way to achieve the result you are looking for, and you may prefer one tool over another.

The regular lasso tool allows you to make freehand selections. Just click and drag, drawing around the area of the photo you are interested in to make your selection. Whenever you let go of the mouse button, the selection will automatically close, forming a straight line between the start and end points. This can be a little irritating if you haven't actually finished drawing around the area you wanted but it isn't really a problem. Just select the "add to selection" option from 4 options on the toolbar and click and drag around the area you missed to top up the selection. You will regularly use these option buttons to refine your selection anyway, by adding small areas you missed and slicing off areas that you don't want (using the "subtract from selection" option. The shortcuts for adding to and subtracting from the selection are the same as the marquee tools i.e. hold shift while dragging to add to your selection and hold Alt/Option when dragging to subtract from your selection.

The Polygonal Lasso tool is used to draw straight line selections. You can make the polygonal lasso tool work just like the regular lasso tool by holding down the Alt/Option key to draw freehand selection. An additional feature of the Polygonal lasso tool is that you can use the Shift key to constrain the selection lines to 45° increments. If you are drawing a straight line selection you can also press the delete key at any time to remove the last segment. To remove multiple segments, press delete repeatedly. Be very careful that you haven't completed the selection before you press the delete key or you will actually delete that section of the photo! It is easily recovered using the history pallet or the undo button from the edit drop down menu.

If you used the polygonal lasso tool to make a freehand selection you can hold down the delete key to slowly erase the line. This also requires a bit of coordination, because you will have the Alt/Option key already held down to draw freehand. What you need to do is let up on the Alt/Option key and hold down delete. Then when you have erased as much as you'd like, you can go back to pressing down the Alt/Option key to continue your selection in freehand mode.

The Magnetic Lasso tool works in a similar way to the other lasso tools, but it has a special feature that allows it to detect areas of contrast and it clings to the edges of the object you're trying to select. Because of this feature, the magnetic lasso has more options than the other lasso tools and you can see these at the top of the toolbar when this tool is selected.

The lasso width controls how close to the edge you need to stay as you draw around the part of the photo you want. Frequency controls how often points are laid down, and edge contrast helps you to fine tune the edge detection. You should play around with these options to see how they can be used to help you make selections more accurately. As you drag along the edge of an object, the tool drops fastening points to anchor the selection.

If you get too far away from the edge, you may get a point in the wrong place. You can back up and remove points by clicking the delete key as you use the magnetic lasso tool. You can also add points manually by clicking once where you want to place a point. When you get all the way around your object, your cursor will change to show a small circle next to it. Clicking once will close the selection and you'll see the "marching ants" selection marquee surrounding the section of image you selected. Depending on how precise you want your selection to be, it is a good idea to zoom right in on the edges so you can see how well the tool has stuck to the edges. You can then make the customary refinements to your selection using the add/subtract options and whichever is your preferred lasso tool.

You can temporarily switch to the regular lasso tool behaviour while using the magnetic lasso by holding down the Alt/Option key and dragging or you can switch to the polygonal lasso tool behaviour by holding down the Alt/Option key and clicking. The Delete key allows you to delete points.

There are also some advanced lasso tool shortcuts that you can use to make adjustments to the lasso attributes while you are actually using the tool, but we don't find them particularly useful in photo restoration.

You can adjust the lasso width as you draw using the arrow keys or the [ and ] keys, you can adjust the frequency that anchor points are laid as you draw using the ; (semicolon) and ' (apostrophe) keys, and you can adjust the edge contrast as you draw using the , (comma) and . (period) keys.

You can close selections with the polygonal lasso and the magnetic lasso by double-clicking with the mouse or pressing the return key. This then draws a straight line from the last selected point and the first selected point.

As with the marquee tools, another very useful option to consider is "Feather". This allows you to soften the edges of your selection so that any changes you make blend in much better with the unaffected areas of the image.

Have fun as you develop your skills and don't be afraid to try new things - the undo button and the history pallet are your friends!