• Holding the Option (Mac) / Alt (Win) key while dragging with the Marquee tools creates a selection from the center.
• Holding the Shift key will constrain the Marquee to a square or circle.
• After starting to draw a selection, holding the spacebar (while still holding the mouse down) allows the repositioning of the origin of the selection. Releasing the spacebar (while still holding the mouse down) allows continuation of drawing of the selection.
The Marquee, Lasso, Magic Wand and Quick Selection tools all share some common shortcuts that can help you when making more complex selections (Instead of using the icons in the Options bar):
• Holding the Shift key and dragging with the tool will add to an existing selection.
• Holding the Option (Mac) / Alt (Win) and dragging with the tool will subtract from the original selection.
• Holding the Option (Mac) / Alt (Win) + Shift and dragging with the tool will produce the intersection of selections.
• After creating a selection, you can move a it by 1 pixel with the arrow keys. Add the Shift key to move in increments of 10 pixels.
• Holding the Shift key after beginning to move a selection or layer will constrain the movement to multiples of 45° (0°, 45°, 90° etc.).
Change preview settings for Layer thumbnails by selecting Panel Options from the Layers panel flyout. Select a desired Thumbnail Size (note: if your image is significantly wider than it is high, selecting the smaller icon sizes might display the generic icon for Adjustment layers more often). Choose Change Thumbnail Contents to either “Layer Bounds” (in general this will display a larger preview of layers containing minimal content), or to “Entire Document” (which will generally display layer content smaller, in relationship to the entire document). Choose “Use Default Masks on Fill layers” to automatically add masks to Fill layers and “Expand New Effects” to display the contents of layer styles when applied.
To delete a layer(s), select it in the Layers panel and tap the delete key. To delete hidden layers from the Layers panel, use the fly-out and select Delete Hidden Layers.
Option (Mac) / Alt (Win) -click on a layer's eye icon to hide all other layers, Option (Mac) / Alt (Win) -click again to toggle all previously visible layers. To make all layers visible (as oppose to only those that were previously visible), Control (Mac) / right mouse (Win) -click the layer's eye icon and select “Show/Hide all other layers”.
Command (Mac) / Control (Win) + Shift + N will add a new layer and display the New Layer dialog box. Add the Option (Mac) / Alt (Win) to add a new layer without displaying the dialog.
I neglected to say that simply draging the lock icon from the Background layer to the trash will convert a Background to a layer - Thanks to Jeff Tranberry for that additional shortcut!
Double clicking on the “Background” layer in the Layers panel will display the New Layer dialog box - changing the Background into a layer and giving you options such as the ability to rename the layer. Option (Mac) / Alt (Win) -double clicking on the “Background” will change the “Background" into a layer - bypassing the dialog box. If you choose the second option, and then need to rename the layer at a later time, simply double click the layer’s name in the Layers panel to rename it.
When aligning layers, it’s best to turn on Smart Guides. Use the Move tool to reposition the layers - Smart Guides automatically appear when they are aligned at top, center, bottom, left or right.
To change the image size of a document and have the guides in the image resize proportionally, be sure to unlock them by unchecking the View > Lock Guides menu item. If you need them to stay in place, then lock the guides before resizing.
Place a guide numerically using View / New Guide and Lock using View / Lock Guides or Command + Option (Mac) / Control + Alt (Win) + “;” . And finally, when dragging out a guide from the rulers, Option (Mac) / Alt (Win) toggles the orientation of the guide (vertical to horizontal).
To change the image size of a document and have the guides in the image resize proportionally, be sure to unlock them by unchecking the View > Lock Guides menu item. If you need them to stay in place, then lock the guides before resizing.
To reposition a guide using the Move tool, position the Move tool directly on top of the guide. When the icon changes to a double headed arrow, click and drag to reposition the guide. Drag a guide outside of the image area to quickly delete it. Shift-drag a guide to snap it to the ruler tic marks even is the “snap to” option is turned off (View / Snap To...).
Since yesterdays shortcut had to do with the Eyedropper, it makes sense to me to follow with shortcuts for the Color Sampler tool. With the Eyedropper tool selected, Shift-click in the image area to set a Color Sampler. With the Eyedropper tool or the Color Sampler tool selected, Option (Mac) / Alt (Win) Shift-click on the Color Sampler (the icon will change to a pair of scissors) to delete.
The Eyedropper has been relocated to the first grouping of tools in the tool box. In addition, it has been refined n Photoshop CS4, allowing you to choose to sample the Current Layers or All Layers (in the Options bar). The eyedropper’s “Sample Size”, set in the options bar, affects the Magic Wand, Magic Eraser and the Background Eraser. Option (Mac) / Alt (Win) click the Eyedropper to select the background color swatch (instead of the foreground) in the Tool panel. In addition, in Photoshop CS4, the Eyedropper can sample a value of a color within a Smart Object. The eyedropper can now sample colors from outside of Photoshop. Make the color visible (on the desktop, in another application etc.). Then click with the eyedropper on the image and then drag to sample the desired color.
Each tool has its keyboard shortcut - B = Brush, C = Crop, M = Marquee and so on. In previous versions if you had a tool selected and wanted to select a second tool to use for a moment, and then return to the first tool you had to tap the second tools shortcut and then tap the first tools shortcut to return to it. Now, with spring loaded cursors, instead of tapping the desired tool, you hold the shortcut down while you use the tool, and when you release the key, you will automatically be returned to the first tool! For example you are drawing a path with the pen tool but need to change the rotation of the view - press and hold the “R” key (for rotation) and after rotating the view, release the key - you are back with the pen tool, ready to go!
When I have several images that are all tiled and I need to zoom in or out on one of them without changing the size of the window, I toggle off Preference / General / Zoom Resizes Window. If you prefer to leave your preference toggled on, then you can temporarily stop the window from resizing by adding the Option (Mac) / Alt (Win) key to the old standby - Command (Mac) / Control (Win) “+” (plus) to zoom in, Command (Mac) / Control (Win) “-” (minus) to zoom out. If I remember correctly, I believe that this default behaviors are reversed on the Windows platform (ie zooming doesn’t resize the window by default) but you can still customize your preference on either platform.
The Tool Box can be displayed as either a single or double column. Clicking the double arrows at the top of the tool box will toggle their layout. Any tool in the toolbox can be selected with a single letter shortcut key. Type that letter, get that tool. Some tool slots in the toolbox have more than one tool in them. If you want to cycle through nested tools hold the Shift key and type the shortcut for the tool. If you prefer to cycle through the tools in a group without using the Shift key, this option can be turned off by selecting (Mac) Photoshop > Preferences > General (Windows) Edit > Preferences > General) and unchecking “Use Shift Key for Tool Switch”.
The point of origin (or the starting or zero point of the rulers) can be changed by simply clicking and dragging the box in the upper left corner of the rulers (where they meet) to reposition. Double clicking at the intersection of the rulers resets the point of origin to the upper left corner of the open document.
In order to quickly find the center of an image, set the rulers to percentage. Setting the rulers to percentage can also be helpful when recording action that will be run on files of different sizes where you might want an effect to be applied to a certain percentage of an area.
Use Preferences / Guides, Grid & Slices to control the Style, Color, and Grid line spacing and subdivisions. Yes, this means that guides can be a soothing neutral gray, not Cyan or Magenta!
To change Ruler units, double click in the ruler area to display the Units & Rulers preferences dialog box, or Control (Mac) /right mouse (Win) the ruler area to access units from the context sensitive menu.
To quickly display rulers at the top and left of an image, click the View Extras icon in the new Application Bar in Photoshop CS4 and select Show Rulers from the drop down menu, or use the keyboard shortcut, Command (Mac) / Control (Win) + R to toggle the rulers visibility. Command (Mac) / Control (Win) + “;” toggles the visibility of guides and Command (Mac) / Control (Win) + ‘ toggles visibility of grids.