Precision Cloning

This is a quick tip but I found it very useful recently. Say you need to clone out parts of an image, e.g. other tourists at a popular spot. Let's also say that the background has fine details that will be obviously wrong if the don't line up just right (e.g. a railing, fence, building, or anything with straight, horizontal edges).

In case you're not familiar, cloning is simply painting from one part of an image onto another part of the same image, using the "clone tool" in Photoshop. It works like a paintbrush, only instead of painting with color, you're painting with the pixels from the "source" part of the image, which you choose.

The tip is to use a guide to place both your source and destination clicks. Drag a guide down from the top ruler to the spot where you want to place your source click. Hold down option (or alt on PC) to get the source crosshairs and line the horizontal line up right over the guide, and click. Then follow the guide to your destination, hold option (alt) again, line it up, and this time let go of option (alt) without moving the mouse at all. Now click, hold, and paint. Your cloned pixels will line up perfectly with the source pixels.

This works vertically too, of course, with a vertical guide.