Saturday, December 09, 2006

Photoshop Tip: John's Shortcuts for Cropping

With a 24-inch screen and a DSLR that takes super-sized pictures, cropping is more of a concern than it used to be. Here's some Photoshop advice to make the process simpler.

  • Use the Marquee tool to make a rectangular selection, then the Image->Crop menu choice, rather than the Crop tool. Using a selection gives more flexibility than the Crop tool, for example the ability to make a selection with a fixed size or to save selections as alpha channels.
  • If you plan to make a photo print of the picture, make a selection with a fixed aspect ratio of 6x4, 7x5, 10x8, or whatever dimensions you plan to use for the prints. Reverse the numbers for pictures printed in portrait style, i.e. taller than wide.
  • If you need to have different-sized crops of the same picture -- for example, to print both a 4x6 and make an 8x10 enlargement -- make the selection and choose the Select->Save Selection menu item. Save the selection as an alpha channel. You can make several selections this way with different sizes, save them as part of your .psd file, then later do Select->Load Selection and Image->Crop. Just remember to always save the file under a different name after you've cropped it.
  • If you will be projecting the photo or displaying it on a laptop, crop using an aspect ratio that matches the projector or laptop. For example, my local photo club uses a projector with 1024x768 resolution, so I crop competition photos to an aspect ratio of 4x3. That way, I can always resize the cropped image to 1024x768 and not lose anything.
  • For pictures where the subject doesn't take up a lot of the frame, such as a wildlife shot taken from a distance, consider doing an initial crop to match the dimensions of your monitor. You'll need to use the rectangular Marguee technique with options set to a fixed size. That way, you can do the rest of the work looking at the picture at 100%, and only later decide whether to crop even more. This technique works best if your screen resolution is greater than on the projector, laptop, etc. where the picture will end up. For example, I do my photo editing on a 1900x1200 screen but typically display slideshows on a 1280x960 laptop. If I am reviewing and working on dozens of surfing pictures where the surfer is surrounded by lots of ocean, I can work faster and save disk space by cropping out lots of blue. Using an absolute size of 1900x1200 means I don't have to worry about cropping out too much, there's always some excess to trim later.
  • Once you've made a selection, you can preview how the cropped version will look by pressing Q to go into Quick Mask mode. The part of the picture outside the selection turns red, so you can visualize how the photo will look without the extra parts, the same as when you select with the Crop tool and it darkens the unselected portion. Quick Mask mode has many other uses, but for cropping purposes, just press Q again to go back to normal.
  • Once you've made a selection, you can resize or move it with the Select->Transform Selection menu choice. Press Enter once you are satisfied. By default, the transformation ignores any size or aspect ratio options; hold down Shift while resizing to keep the selection consistent with those options.
  • I find it inconvenient not to have keyboard shortcuts for Image->Crop and Select->Transform Selection. In Photoshop CS, you can assign your own keyboard shortcuts with Edit->Keyboard Shortcuts. Photoshop already has shortcuts using most combinations of letters and modifiers, but whatever operations used Shift-Command-C and Command-T, I never used 'em and so reassigned them to Image->Crop and Select->Transform Selection.

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