Adobe Photoshop CS5 for Photographers : The Ultimate Workshop



Perspective crop tool

The perspective crop tool can be used to crop and correct the converging verticals or horizontal lines in a picture with a single crop action. In Figure 1 I wanted to correct the converging verticals or ‘keystone’ effect seen in this photograph. Using the perspective crop tool I was able to accurately reposition the corner handles on the image to match the perspective of the building. In Photoshop you can either marquee drag with the tool as usual, or click to define the four corners of the perspective crop, after which you can drag on the corner and/or side handles to adjust the crop shape. Having done this you can click to confirm and apply the crop and, at the same time, correct the perspective. The perspective crop should work well in most cases, but you may sometimes need to apply a further transformation to compensate for any undesired stretching of the image.

Figure1 The perspective crop tool is great for correcting perspective. You will mostly find it easier to zoom in to gauge the alignment of the crop edges against the converging verticals. Here, it was also useful to check the ‘Show Grid’ option to help adjust the alignment correctly. Note also the ‘Front Image’ button. Clicking this loads the current document full image size dimensions and resolution settings, so that when you apply the crop the cropped image retains the same size (but may well appear stretched of course). It can also help here to switch on the Grid display (go to the Window menu and choose Show Grid).

Modifying a perspective crop

When the perspective crop bounding box is active you can modify the crop shape by dragging the corner or side handles. If you hold down the Shift key as you drag a handle this constrains the movement to vertical or horizontal plane movement only. If you hold down the Option/Alt key as you drag a corner handle this allows you to resize the crop in both planes at once. If you hold down the Option/Alt key as you drag a side handle this allows you to expand the crop equally both sides at once.