Getting Before And After Previews
If you're applying a correction filter, such as the Unsharp Mask filter, you can get a before and after view of your image even before you click the OK button (and then press Command-Z [PC: Control-Z] to undo/redo the filter). Instead, click-and-hold on the preview box inside the Unsharp Mask filter. When you click-and-hold, you get the before preview in the window; when you release the mouse button, it shows you how the image will look with the filter applied. Pretty handy. If you need to see the full preview onscreen, you can toggle the Preview checkbox on or off. Another tip is to hold the Command or Option (PC: Control or Alt) button while in a filter dialog, and then your cursor changes into the Zoom tool. You can then zoom in or out in your preview window by clicking within it.