Last month, I explained how the marquee tools create selections, permitting the digital artist to apply alterations to portions of an image. For anyone who tried applying these techniques, however, a problem quickly presented itself. Unless the subjects contain only straight lines or ovals, the marquee tools are of limited use for photographic selections. It is true that the rectangular marquee can be a valuable tool for architectural photography, but for the nature photographer it serves no real purpose. After all, how many square shaped animals do we see while out in the field (box turtles do not count)?

The solution is to use different selection tools based on the type of selection needed. Having just moved back to Texas, I though it would be appropriate to begin with the lasso tool. Located on the tool bar directly under the marquee tool, the lasso tool icon depicts a rope lasso flying through the air. For those of you who enjoy shortcuts, the lasso tool can be selected by pressing "L."

In reality, three different lasso tools exist: the lasso, the polygonal lasso, and the magnetic lasso. To access all three tools, click and hold the mouse over the lasso tool on the toolbar. Once the dropdown menu appears, select the tool desired and begin the selection. Another method for scrolling through the different lasso tools is to press Shift + L until the desired type of lasso is selected.

The Lasso:

The lasso is the most basic and intuitive of the lasso tools. To create a selection, hold the mouse button down and draw any shape desired. To complete the selection, release the mouse. Be warned, however, that releasing the mouse will create a straight line between the point of release and the original start point for the selection. For best results, I advise ending a selection by completely enclosing the selected area, so that the start and end points overlap.

The advantage of using the lasso for selections is that you are not limited to a specific shape. Twists and curves are no longer selection nightmares, but simply new shapes to be included. With the lasso tool if you can trace it, you can select it.

The Polygonal Lasso:

Thinking back to basic geometry, a polygon is any shape containing multiple sides. Pentagrams (5 sides) and octagons (eight sides) are both examples of polygons. The polygonal lasso tool acts as a sophisticated marquee tool, creating selections that have many sides. Unlike the lasso tool which follows the path that is traced, the polygonal lasso uses anchor points to create its selection. Click at any point to begin the selection process. Each subsequent click creates a new anchor point with a straight line connecting the new point to the previous point. The selection is completed by double clicking the mouse which creates a final anchor point that is attached to both the previous anchor point and the staring anchor point. In case of mistakes (they will happen) anchor points can be removed by pressing delete. In effect, the polygonal lasso functions like a connect-the-dot game where the dots are created as I go along.

On the surface, the polygonal lasso is a neat idea, however, it has limited application for nature photographers. Like the marquee tool, the polygonal lasso creates selections with straight lines, not curves. This pattern works well for architecture and signs, but has fewer applications for photographers who shoot others subjects.

The Magnetic Lasso:

The magnetic lasso acts as a combination of the lasso and the polygonal lasso with a bit of artificial intelligence thrown into the mix. Like the lasso, the magnetic lasso works by tracing the part of the image to be selected. As the object is traced, Photoshop applies anchor points around the subject, creating a remarkably accurate selection. Good basic selections can be crated even by those of use who have difficulty tracing the simplest shapes. Like the polygonal lasso, errors can be removed with the delete key and a double click will finalize a selection.

The magnetic lasso works by analyzing image contrast. Unlike 3-D objects, photographs are two dimensional. The edges of objects within a photograph take on a 3-D appearance because of contrast. Edges are visible because they are areas of high contrast (light on one side and dark on the other). Our eyes define these areas of contrast as edges and use them to impose a sense of depth to the image. The magnetic lasso also identifies these areas of high contrast and labels them "edges." Once edges are identified, anchor points are set down along the edge. This simple, but effective concept does have its limits, however, in images where the edges are not clearly defined. Imagine a photograph of a penguin standing in front of a dark rock. In terms of edge contrast, the white feathers of the bird stand out while the dark feathers blend into the background. In this case, the magnetic lasso would have no problem selecting the white areas, but the black areas would present a problem. Most likely, the selection would include parts of the rock while cutting off portions of the dark feathers. When strong contrast exists between the subject to be selected and the rest of the image, the magnetic lasso tool is ideal. When little contrast exists, a different selection tool will likely produce superior results.

Creating Good Selections:

The key to good selections is NOT making a perfect selection right from the start. Instead, begin with a rough selection that can subsequently be modified. Previously, I discussed how selections can be modified through the use of the Shift and Alt (option) keys. Holding down shift adds to the current selection without loosing what has already be done. Pressing Alt subtracts from a current selection. By adding and subtracting it is possible to fine-tune a rough selection into a good selection that isolates the desired area.

A good selection takes time, but there are a few tips and tricks that can help along the way.

• Enlarge the image. Tracing fine detail is much more difficult when it is small. Before making a selection, press Ctrl (Command) + "+" a few times to zoom in on the image. Lines become clearer and easier to follow. To move around the enlarged image, press the spacebar to active the hand tool. With the spacebar pressed, hold down the mouse button and move around the image. Releasing the spacebar reactivates the selection tool.
• I find that the stead hand and focused concentration needed to create complex selections with the free-form lasso is difficult to maintain for long. Instead, I like to create rough selections using any of the tools available (magnetic lasso, magic wand, etc.) and then fine-tune them with the lasso. Quick selection touch ups are what the lasso excels at.
• Free form drawing with a mouse can be challenging. For better results, consider investing in a Wacom stylus that more closely mimics a pen and paper setup.
• Don't think that a selection has to be created with only one tool. I frequently use a variety of different tools to create a single selection. By using Shift and Alt, the previous selection is maintains and alterations are applied.
• ALWAYS leave the option bar's feather amount set to 0. There is a good reason for this, but the explanation will have to wait for a future article.

The lasso tools provide a simple, intuitive way to create relatively complex selections. They are ideally designed for selecting sharp, irregularly shaped edges that commonly occur in photographs.

Chris Gamel has been an active wildlife photographer for the past 14 years. The combination of his biological research and photographic interests has taken him around the world. In 2001, Chris discovered the joys of digital photography and he hasn't looked back. Chris lives with his wife and daughter in Salt Lake City where he teaches courses at Weber State University and Salt Lake Community College. To see more of Chris's photography, visit his web site at www.Animal-Antics.net.

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