This chapter is from the book
This chapter is from the book
This chapter is from the book
Refining Selections
The goal is to create a perfect selection, but in practice this is hard to do. The most typical workflow is to create an accurate selection and then refine it. Photoshop offers several ways to improve upon an initial selection. The method you choose is really a matter of personal preference.
Refining Basic Selections
When you have most of your desired pixels, you can pick up little stray pockets by using the Select menu. There are seven additional options available in all versions of Photoshop that are useful. They’re available for all selection tools and methods.
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Grow: This expands your selection by choosing pixels that are both adjacent to the current selection and resemble the colors in the current selection. The selection will grow based on the tolerance setting you have in the options bar for the Magic Wand tool.
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Similar: This command works like Grow, except pixels need not be adjacent to the current selection.
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Contract: This pulls the active selection inward a specified number of pixels.
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Expand: This pushes the active selection outward a specified number of pixels.
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Smooth: This useful command rounds out selections and gets rid of sharp corners. Specify an amount as a sample radius (larger numbers mean smoother edges).
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Border: This command uses the current selection to create a new area of a user-specified thickness that borders the previous selection. It’s limited in its practical applications, but it can be useful for video pros to “defringe” an object. If your object has rough edges, you can load the object and then use the border selection to specify a thin 2- or 3-pixel border. This area can then be deleted or blurred. (Think of this as “choking the matte.”)
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Feather: The final step of most selections is feathering. This generates a graduated edge. Think of feathering as the difference between a ballpoint and felt-tip pen.
Reselect a Selection
Want to go back to your last selection? Photoshop stores your last selection in RAM. As long as the current document is open, you can choose Select > Reselect or press Shift+Cmd+D (Shift+Ctrl+D).
Refine Edge Command
While the Select menu offers several options, there is always room for improvement. Starting with CS3, Photoshop has offered a powerful option for refining a selection. The Refine Edge command can be accessed two ways. It’s available in the options bar for all selection tools. It can also be chosen from the menus by choosing Select > Refine Edge. This command is very intuitive, and its sliders provide quick feedback as you refine a selection.
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- Open the file Ch04_Refine_Edge.tif from the DVD.
- Switch to the Channels panel, and Cmd+click (Ctrl+click) the alpha channel to load it as a selection.
- Choose Select > Refine Edge. (You can also click the Refine Edges button in the options bar if a selection tool is active.)
- Click the View button to change the viewing mode for how the selection is displayed (or use the corresponding keyboard shortcut).
Try the different modes to see the results.
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Marching Ants (M): Shows the selection with the started dashed line.
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Overlay (V): Behaves similarly to the Quick Mask mode.
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On Black (B): Previews the layer over black, which is good for light edges.
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On White (W): Shows the selected region over a white background.
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Black & White (K): Simulates a channel view where the selection displays as a black (transparent) and white (opaque) layer, with gray indicating partial transparency.
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On Layers (L): Composites the image over any other layers (or transparency if it’s a single-layer image).
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Reveal Layer (R): Shows the entire, original layer contents.
Change Your Refined View
To cycle through the different viewing modes in the Refine Edge dialog, just press the F key repeatedly. If you’d like to temporarily disable the view, press the X key.
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- Next, you can use Edge Detection to clean up the edges further. These controls work best for areas of partial transparency.
Experiment with Edge Detection to improve the selection.
Smarter Refinements
You can use the Show Radius and Show Original check boxes to make it easier to see the changes created with the Edge Detection options.
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Radius: Drag to refine the selection edge. Try a value of 8 for this image.
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Smart Radius: This option automatically evaluates contrast in the edges and attempts to correct for better transitions. If your object lacks uniform hardness and softness, use this option. Turn on this option for this image (and in most cases).
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Refine Radius tool: Use this brush-style tool to paint over any edges that need additional refinement. You can also hold the Option (Alt) key to switch to an erase mode to undo any unwanted refinements.
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- The next group of sliders allows you to adjust the edge globally. Experiment with the following sliders:
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Smooth: Removes any jagged edges.
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Feather: Softens the edge of the selection.
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Contrast: Increases the contrast of a selection’s edge. You’ll get better results, in most cases, with the Smart Radius and refinement tools.
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Shift Edge: Grows or shrinks a selection. This is a quick way to tighten a rough selection and remove color spill.
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- The last category, Output, determines how the processed selection is treated.
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Decontaminate Colors: Applies color correction to remove any color spill from the background onto the selected object.
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- Finally, you’ll need to determine what Photoshop does with the new selection. The choices are many (and useful):
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Selection: Creates an active selection.
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Layer Mask: Creates a nondestructive mask that creates transparency in the highlighted layer.
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New Layer: Creates a new layer with only the selected area.
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New Layer with Layer Mask: Creates a new layer with only the selected area masked. This is the most flexible option. Choose this option for this document.
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New Document: Creates a new document with only the selected area.
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New Document with Layer Mask: Creates a new document with the selected area masked.
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- Click OK to create the selection and masked image.
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Quick Mask Mode
The Quick Mask mode is another one of those overlooked features that really should make its way into your skill set. In Quick Mask mode, you can use Paintbrush tools and the Smudge and Blur tools to generate an accurate selection. Enter this mode from a button near the bottom of the toolbox. It’s a good idea to build a rough selection first.
Get Better with Brushes
Masks are very dependent on your paintbrush skills. Remember to practice freedrawing with the mouse or tablet to improve your ability to create brushstrokes.
- Open the image Ch04_Quick_Mask.tif from the chapter folder.
- Use your selection tools to build a rough selection.
- When satisfied, click the Quick Mask icon or press Q.
Depending on user preference, either the masked or selected areas will be covered with a color overlay signifying the masked areas.
Better Edges Through Feathering
Feathered edges are important to creating believable composites.
A feathered edge uses graduated steps to go between selected and unselected. Think of it as the difference between a ballpoint pen and a felt-tip marker. You can feather after making a selection by going to the Select menu and choosing Feather. You can feather up to 250 pixels, but the amount needed will vary based upon the resolution of the source image. You can also modify the Marquee tools to have feathered edges. Experiment with feathering to improve your selections.
- Now you need to clean up the quick mask. To start, press the D key to load the default colors, pure black and white.
When you create the quick mask (or any mask), using black will add to the mask, and white will subtract. If you use the brush at less than 100% opacity, you’ll generate feathered edges.
- It’s a good idea to paint as close as you can with a large, soft brush. You can make your active brush larger by pressing the right bracket key (]); the left bracket ([) will reduce the brush size. To soften the edges of your brush, use the Shift and [ or ] keys.
- The final touches to a quick mask come from the Smudge and Blur tools. Adjust the pressure setting to a low value. Zoom in so you can clearly see your edges. By employing a series of short strokes, you can touch up the soft edges of your mask.
- As you work your way in to the finer parts of the mask, particularly soft edges, it’s a good idea to zoom in. While painting,
holding down the spacebar will temporarily switch you to the Hand tool. This makes it easier to move around the work area
without having to slow down.
You can also place the Navigator panel in plain view. The red box signifies the current view area and can be dragged around easily. The Navigator gives you a visual interface to the work area.
- When you’re satisfied with the quick mask, click the icon or press Q to turn the quick mask into a selection.
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