The Crop Tool in Photoshop CS2

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.