The goal in cloning is to take part of the image in good shape, and partially or completely paste it over the defect. The image you are pasting from does not need to be on the same photo, although it is usually more convenient to do so. In this case, I'll demonstrate pasting over the defects using the clone command. The image below shows a screen shot using the clone command in Picture Window. In some of the photo editing programs, this will be known as the rubber stamp command.
This shows a couple of tricks I use for cloning. First, notice the picture is zoomed way in. I like to get to the point that I can see individual pixels. Second, Picture Window has a "magnifier, that shows the current photo at any magnification you want. Sometimes what looks great at the pixel level does not look so great when you zoom back out (especially if you get repeat patterns accidentally) - the magnifier gives you a preview of what the photo will look like. The two circles by the eye are the cloning "brushes"; the circle with the dot is where you are copying from (set it by shift-clicking), and the other circle is where you are copying to. I usually will have the transparency slider in the clone command set to more than 0 (i.e. the copy appears somewhat transparent over the area on which your copying), and the softness set to about 50% - both of these allow some blending of the cloned image into the original image.
In the screen shot above, I have the open circle over a blemish that I wish to remove, and the target to copy from set over a portion of skin with similar texture and similar level of brightness. Then, it is simply a matter of clicking on the blemish to copy the new image over it. This is easy for small blemishes such as the one above, where the texture is not so obvious that misaligning the texture will be immediately obvious. The next screen shot shows the result for this and some of the area on the nose.
So compare the spots on the eye and the bridge of the nose to the screen shot above. As I was writing this, I looked for the fix above the eye shown in the first screen shot, and figured I had found it - only to find that I was looking at part of the original photo and not the fix. The cloning blends in well. The area I was working on in this shot was the spots in the nostril.
I'm told some people use the paint command, select the proper skin tone, and then select a brush to simply paint the tone into the defect. I have not had good luck with this maneuver, since it does not recreate the texture. Skin has texture, and film has grain, so that any area of significant size that has a perfectly smooth tone without any appearance of texture will usually be pretty obvious on the final image.
So I cheat - I find an area with similar brightness and texture, and paste it in using the clone command. This will give you that textured look without while filling in the defects.
Now we get to the tough part; filling in the cheek. Oh, no problem, you say? Well, there is. The cheek is showing a nice gradation from shadow to light, which we will have to try hard to duplicate. Also, there is enough damage that there is not very much good area to copy from across the entire range of brightness that we need. One additional helpful tool is shown below.
In this screen shot I'm working on the right cheek on a larger defect than the previous ones. I've brought up another tool to help - the readout tool This tool simply gives the RGB values (for a monochrome image, the levels for red, green, and blue should all be about equal, as you can see in the readout window above), which I use to measure the brightness of a particular area. This is more accurate than my eye at saying part A of the photo is the same level of brightness as part B of the photo. This tool lets me copy from more areas more easily. For example, parts of the cheek that I've cloned in here were actually cloned from skin at similar brightness levels from the forehead. If you are off by even a minimal amount on brightness levels, the area you clone in will stand out if there is a reasonably homogenous tone, such as areas of the cheek. One of my earlier cloning successes was on a photo of the seafloor, which is quite irregular with no pattern whatsoever - if I pasted in something that was not the exact perfect shade, it simply looked like part of the expected irregularity of the sea floor. We can't get away with variation like that case in this instance, however, so I use the readout tool to assist me.
In the larger defects, such as the one I am correcting above, I try to clone into the center from the edges from several different angles, using target areas from several different areas. This technique helps to provide some variation and avoid the weird repeating patterns that you can get from consistently pasting one patch of target area over a large defect area. This repeating pattern comes from subtle changes in the image, but if you keep repeating the subtle changes (sort of like tiling an image for your computer wallpaper), you get repeating patterns from pasting the same small image next to itself. Look at the following worst-case scenario:
I simply cloned over the defects on the cheek, starting on the right side (mine) of the defect, and continued cloning to the left from an area immediately to the left of where I was cloning to. This meant that as I put down new image, it would recopy to the next portion of the defect. As you can see, it gives a VERY noticeable and repetitive pattern. I get around this by pasting from a number of areas to cover the defects, so that the variation in tones and texture would appear more random, as is the case for the real image, and so I would not get this patterning effect. The downside of this technique is that you need lots of similar areas to copy from. One thing that can be a saving grace is that you do not necessarily have to copy from the same photo (although I usually do unless it is a real emergency), so if necessary you can copy from other photos onto this one (more on this in a moment).
So, let's look at the progress on the photo.