You control the behavior of Photoshop’s tools through the Options bar. With the exception of a few path-related tools (Add Anchor Point, Delete Anchor Point, and Convert Point), every tool in Photoshop has options. The Options bar changes as you switch tools. The behavior of some tools changes when you add one or more modifier keys (Command , Shift, and Option for the Mac; Ctrl, Shift, and Alt for Windows). As an example of how modifier keys can affect tool behavior, consider the Rectangular Marquee and Elliptical Marquee tools:
- Hold down the Shift key while dragging. Normally the marquee selection tools are freeform — you drag however you like. When you hold down the Shift key while dragging, on the other hand, you constrain the proportions of the selection to a square or circle (rather than a rectangle or ellipse).
- Hold down the Option/Alt key while dragging. When you hold down the Option/Alt key while dragging a marquee selection tool, the selection is centered on the point where you first clicked. Rather than being a corner of a selection, that starting point is the center of the selection.
- Hold down the Shift and Option/Alt keys while dragging. You can select from the center while constraining proportions by using the Shift and Option/Alt keys together.
- Use the Shift key to add to an existing selection. If you already have an active selection in your image, Shift+dragging a selection tool adds to that selection. (Press Shift before you click and drag.)
- Use the Option/Alt key to subtract from an existing selection. When you have an existing selection and you hold down the Option/Alt key, you can drag to subtract from the selection. Note in the figure that the selection tool’s cursor shows a small minus sign when subtracting from a selection.
- “Double-clutch” with the Shift or Option/Alt key. You can even constrain proportions or select from the center and add to or subtract from a selection. Press the Shift key (to add to the existing selection) or the Option/Alt key (to subtract from the existing selection). Click and start dragging the marquee selection tool. While continuing to hold down the mouse button, release the modifier key and press and hold Shift (to constrain proportions), Option/Alt (to center the selection), or both; then continue to drag your selection tool. You might want to use this technique, for example, when creating a donut-shaped selection. Drag the initial circular selection and then subtract a smaller circular selection from the center of the initial circle.
Use the Option/Alt key with a selection tool to subtract from a selection.Don’t be afraid to experiment with modifier keys while working with tools. After all, you always have the Undo command (Command +Z/Ctrl+Z) at hand!
If you’re using a current version of Windows, you also have Microsoft Dial Support available, which enables you to adjust brush attributes using the Microsoft Dial (if it’s on your hardware).