Use the Crop controls to set a fixed aspect ratio for the cropping rectangle. The default is Current Aspect. You can choose from several predefined ratios of sides in the list, or enter a ratio numerically. Next to the drop-down list, there is a button for adding your frequently-used ratios of sides to a list.
Use the Rotation control to rotate a picture to a precise angle numerically. Next to the slider, there is a button for setting the picture’s horizon [H] – click it and draw out a line in the picture, and the picture will be rotated so as to make that line horizontal (or vertical, if it is closer to the vertical). The Crop Marks menu contains a list of marks that can be shown in the preview area. To quickly toggle among marks, press [Tab].
Press [X] to flip the cropping frame’s ratio of sides, thus changing the orientation of the crop (between landscape and portrait).
Press [Shift+A] to stretch the cropping frame to the largest size supported by the picture’s orientation—if the cropping frame’s current orientation does not match the picture’s orientation, its orientation is changed to match.
Perspective crop – to straighten a picture’s main subject (for example a sign) as you crop, turn on this option and place the four corners of the crop at the object’s corners.