The Crop Tool in Photoshop

Introducing the Crop Tool

Third button down on the left side of the Photoshop toolbox we find the crop tool. The crop tool has a very easy keyboard shortcut to remember, so you'll rarely need to bother with selecting it from the toolbox. The shortcut for activating the crop tool is C. The crop tool in Photoshop can actually do much more than crop your images. The crop tool can be used to increase your canvas size, to rotate and resample images, and to quickly correct the perspective of an image. Let's start by exploring the most common use of the crop tool... cropping, of course! Open any image and select the Crop tool. Notice in the options bar you have spaces to fill in the desired width, height and resolution for the final cropped image. To the far left of the options bar, you can select from several crop tool preset options. I'll go over the crop tool options and presets a bit later, but for now, if you see any numbers in the crop tool options, press the clear button on the options bar to remove them
There's no need to be precise when making the first crop selection, because you can edit your selection before committing to the crop. If you want exact precision however, you will want to switch to a crosshair cursor. At any time, you can toggle from standard to precise cursors by pressing the Caps Lock key. This works with the painting tools as well. Try it out. You may find that the precise cursor is hard to see in some backgrounds, but it's nice to have the option when you need it.

The Crop Shield and Adjusting the Crop Selection

Pick which ever cursor preference you like and drag out a crop selection on your image. When you let go, the crop marquee will appear and the area to be discarded is shielded with a gray screen. The shield makes it easier to visualize how the cropping affects the overall composition. You can change the shielded area color and opacity from the options bar after you make a crop selection. You can also disable the shading by unchecking the "Shield" checkbox. Notice the squares on the corners and sides of the selection marquee. These are called handles because you can grab onto them to manipulate the selection. Move your cursor over each handle and you'll notice it changes to a double pointing arrow to indicate that you can resize the crop border. Make some adjustments to your crop selection now using the handles. You'll notice if you drag a corner handle you can adjust the width and height at the same time. If you hold the shift key down while dragging a corner handle it constrains the height and width proportions.
You'll find if you try to move the selection border to just a few pixels from any of the document edges, the border automatically snaps to the document edge. This makes it difficult to trim just a few pixels from an image, but you can disable snapping by holding down the Ctrl key (Command on Mac) when you get near an edge. You can toggle snapping on and off by pressing Shift-Ctrl-; (Shift-Command-; on Macintosh) or from the menu View > Snap To > Document Bounds.

Moving and Rotating the Crop Selection

Now move your cursor inside the selection marquee. The cursor changes to a solid black arrow indicating that you can move the selection. Holding the shift key while you move the selection constrains your movements. But that's not all... move your cursor to just outside one of the corner handles and you'll see it change to a double pointing curved arrow. When the curved arrow cursor is active you can rotate the selection marquee. This allows you to crop and straighten a crooked image at the same time. Just align one of the crop edges to a portion of the image that should be horizontal or vertical, and when you invoke the crop, it will rotate the image to conform to your selection. The center point on the crop marquee determines the center point to which the marquee is rotated. You can move this center point to change the center of rotation by clicking on it and dragging.

Adjusting Perspective with the Crop Tool

After you draw a crop selection, you have a checkbox on the options bar to adjust the perspective. This is useful for photos of tall buildings where there is some distortion. When you select the perspective check box, you can move your cursor over any of the corner handles and it will change to a shaded arrow. Then you can click and drag each corner of the crop marquee independently. To correct perspective distortion, move the top corners of the selection marquee inward, so that the sides of the selection are aligned with the edges of the building you want to correct.

Completing or Canceling Crop

If you change your mind after you've made a crop selection, you can back out of it by pressing Esc. To commit to your selection and make the crop permanent, you can press Enter or Return, or simply double click inside the selection marquee. You can also use the check mark button on the options bar to commit to the crop, or the circle-slash button to cancel the crop. If you right click in the document where you have made a crop selection, you can also use the context sensitive menu to finish the crop or cancel the crop. You can also crop to a selection using the rectangular marquee tool. When a rectangular selection is active, just choose Image > Crop.

Cropping Layers - Delete or Hide Cropped Area

If you are cropping a layered image, you can choose whether you want to delete the cropped area permanently, or just hide the area outside of the crop marquee. These options appear on the options bar, but they are disabled if your image only contains a background layer or when using the perspective option.

• The Delete option works like a typical crop — the same as if you used the Canvas Size command to clip the image.
  
  
• The Hide option retains those pixels, but resizes the canvas so they are not visible. This area outside the visible canvas is called "big data" and you can make it visible again by choosing Image > Reveal all. Keep in mind that the hide option requires more memory and disk space when you save the file.

Take a few moments now to practice cropping and manipulating the crop selection using all the methods we've discussed so far. You can return your image to its original state at any time by going to File > Revert.

Crop Tool Presets

Now let's get back to those crop tool options and presets. If you select the crop tool and click the arrow at the far left end of the options bar, you'll get a palette of crop tool presets. These presets are for cropping to the most common photo sizes, and they all set the resolution to 300 which means your file will be resampled. You can create your own crop tool presets and add them to the palette. I suggest you create your own crop tool presets for common photo sizes without specifying the resolution so you can quickly crop to these sizes without resampling. I'll walk you through creating the first preset, and you can create the rest on your own. Select the crop tool. In the options bar, enter these values:

• Width = 6
• Height = 4
• Resolution = (leave blank)

Click the arrow for the presets palette, then click the icon on the right to create a new preset. The name will fill in automatically based on the values you used, but you can change it if you like. I named my preset "Crop 6x4."

Cropping Aspect Ratio

Now when you select this preset, the crop tool will have a fixed aspect ratio of 4:6. You can size the crop marquee to any size, but it will always retain this aspect ratio, and when you commit to the crop, no resampling will occur, and the resolution of your image will not be changed. Because you've entered a fixed aspect ratio, the crop marquee will not show side handles — only corner handles. Now that we have created a preset for a 4x6 crop, you can go ahead and create presets for other common sizes such as:
1x1 (Square)
5x7
8x10
You might be tempted to create presets for both portrait and landscape orientations of each size, but this is not necessary. To swap the width and height values for the crop tool, simply click on the double pointing arrows between the Width and Height fields on the options bar, and the numbers will swap.

Additional Cropping Tips

Anytime you use a number in the resolution field of the crop tool, your image will be resampled. Unless you really know what you are doing, I suggest always clearing the resolution field of the crop options. You can also use pixel values in the height and width field of the options bar by typing "px" after the numbers. For instance, if you have a web site and you like to post all your images at the same size of 400 x 300 pixels, you can create a preset for this size. When you use pixel values in the height and width fields, your image will always be resampled to match the exact dimensions.
The "Front Image" button on the the options bar comes into play if you ever need to crop one image based on the exact values of another image. When you click this button, the height, width, and resolution fields will fill in automatically using the values of the active document. Then you can switch to another document and crop to these same values, or create a crop tool preset based on the active document size and resolution.


Source: About.com