enhanced photo cropping
here is a tip for quickly cropping a Photoshop image to exact dimensions.
in Photoshop you can crop an image precisely to grid lines or to smart guides with the following settings.
set grid size with Preferences>Guides, Grid & Slices
to more easily crop to dimensions that are more evenly factored in terms of higher powers of 2 or 4 (for enhanced pixel integrity), i set a gridline every 256 pixel, with 4 subdivisions. thus it is easier to count in terms of either larger 256 pixel grid squares, or smaller 64 pixel squares. counting squares is a quick way to select grid points into specific proportions like 3:2 or 6:4.
set View>Snap with View>Snap To Guides and Grid
choose View>Show to display Grid or Smart Guides.
(Mac shortcut to display or hide grid is command-apostrophe)
set View>Snap with View>Snap To Guides and to Grid
(if the grid is hidden the crop marquis won't snap to grid lines.)
select the Crop tool and then drag the cropping marquis to the selected grid points. (in the Photoshop CS6 beta, the cropping marquis is accompanied by cues for width and height in terms of selected ruler unit of pixel).
in this example with 256 pixel grid lines, i selected a crop area of 6 by 4 grid squares. (W: 1536 px; H 1024 px).
crop and then hide the grid lines to see the resulting image.
to refine the crop, go back to the pre-cropped image and try to select areas of canvas with Image>Canvas Size from which to more specifically crop to grid lines. you can also use smart guides to help you re-align the grid. for example, if the subject of a cropped image is positioned a little bit too far right, then try to remove a little canvas on the left side of the image so that the grid lines align better with the desired crop. on any edge of the image, you can remove or add canvas accordingly to better align grid lines with a desired crop.
06-crop-to-grid-6x4 [marquis not captured, height and width cues are visible]
[captured with Grab for Mac OS X]