An introduction to retouching and cloning

This detailed example is intended to show you what can be done with the retouching tool option Clone. Cloning can be used to remove scratches or soiling from a scanned analog photo, or to correct hot pixels, stuck pixels or shadows from dirt on a digital camera’s sensor. But in this example we go a step further. The picture is of the main street in the ruins of Ostia, the harbor of ancient Rome:


The nature of the task:
The first question is: What doesn’t fit in this picture?
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That’s right, it’s the people! It’s nothing personal, of course, but … they just don’t go with the two-thousand year old ruins. So the first task is to remove the people from the image and reveal the background which is obscured by them. If the photo had been taken using a tripod and another image had been taken after they had moved on, we could simply copy and paste the missing background from the second image:



Section from (fictitious) second photo without people at the same location:



Fictitious section as background for target image:

Sadly, no such second photo exists! So we have to look for an alternative approach.

The basics of cloning:

General information about the image: This picture consists of pixels which all lie in one ‘layer’. What is actually behind the people is unknown to us and cannot be restored as it really is – if we just cut out the pixels making up the images of the people, all that is left is a white hole! But what we can do instead is to use cloning to create a background which appears plausible:



Retouching: the cloning tool

In principle, cloning means copying a section of an image from one part of the image to another, i.e. to paint over the existing image at the new location.
Incidentally, PhotoPerfect can clone from one image to a different one. But this example involves cloning within a single image.
The setting ‘fixed’ next to the "Clone source" option allows you to nail down the source section. That means that always this same image section is pasted. But in our example we wish to clone image sections which vary in size and form. There will be a great deal of ‘trying out’ to see what appears natural, so the ‘fixed’ setting is not appropriate here. Alternatively you can also use the clone destination option.

Clone source vs. Clone destination option:

Whereas "clone source" always uses the original photo before any change as source, "clone destination" in contrast also includes current changes.

Clone source: PhotoPerfect always extracts the clone source from the original state of the image

Clone destination: PhotoPerfect extracts the clone source from the current state of the image

For example, if you are using the clone source option and moving your brush into an area that you have already cloned before, then it will ignore the changes and just use the original details prior cloning as source. Thus usually clone destination option is the more suitable option, as it is WYSIWYG. What you see in the currently selected source area will be used.



The yellow circle marks the source area, the white one marks the position of the clone brush. Now just hold the left mouse button and move from left to right. Below is the difference between the 2 cloning options.




Before cloning:

The only operation which can be sensibly performed before cloning is that of clipping the image edges. All other improvement operations are better done afterwards. For instance, the starting image is practically unsharpened, and it is much easier to clone an image with soft color gradients. Also, reducing the image afterwards will help to reduce cloning inaccuracies, which tend simply to disappear.

Cloning options:

Selecting the right clone brush size:



image section at 1:1 zoom level
As you can see, the standard clone brush has a transparency gradient. I.e. it becomes more unsharp with increasing size; small brushes have almost sharp edges. The size must be selected in accordance with the type of cloning. Usually you will need some degree of unsharpness at the edge of the brush so that the transitions are not too conspicuous and the results are not too obvious.
The more often you click on the same place, the more the transparency is reduced up to the point where the colors are transported without any loss. This example mainly used a brush of size 15. Only where the path becomes very narrow was a size 8 brush used.
There are other possible brush settings which, however, aren’t needed in this case. So here is just a short excursion to describe the different clone options:



Free brush options


The Define brush button allows you to define a polygon representing any shape and size of brush. If a brush is defined, the box next to free brush shape is checked, meaning that it will be used. The soft and transparent boxes can be used to give the brush soft edges or make it 50% transparent, or both together.
In this example, the soft and transparent options have no effect on our round standard brush!
The visible box determines whether the clone brush is to appear as an empty ring or as an area showing the image section which is being used for cloning.

Cloning procedure:

First the image section must be defined which is to be pasted over another part or parts. This is the clone source used for cloning. Please note that this is another term than the clone source option. To do this, keep the CTRL key pressed which left-clicking on the desired position. Note the lower window in the cloning tool: It now shows the clone source with the cross hairs as the midpoint of the clone cursor. You can use the right mouse button to restore places which have already been painted over – but only as long as the retouching dialog remains open. After that only certain steps of the cloning procedure can be undone using the PhotoPerfect’s general Undo function.
Here’s another tip on that score: When you have completed a certain amount of work and are satisfied with the result, close the retouching dialog. Then you can restore that state using PhotoPerfect’s general Undo function at any time during the main session.
The following image resulted from selecting brush size 15 and then the clone source by clicking somewhere on the path in the foreground. Then the path can easily be extended by painting over the people’s legs. If you fail or make any mistake during cloning, thus use the right mouse button or click on Undo to get back. Otherwise click on Accept to save your work.

In this way parts can be pasted in from all over the image, whereby they should approximately match in terms of brightness, color, sharpness, orientation, size etc. Thus it is not a good idea to extend an expanse of ivy with a section having much smaller leaves, or one which catches the sun at a different angle, for instance.
In the following picture you can see how the clone source was selected from the left of the left-hand woman and then used to … well … ‘decapitate’ her ;-)

Also, the wall has been extended. In any such action, it is important to make sure that lines are continued correctly. Thus in this case the slanting top of the wall has been continued in one action, whereas the bricks were cloned separately to provide the horizontal extension. And the bricks were chosen from different places so that the effect is not too uniform.

And so it goes on. You will need a little creativity to be able to make all the sections of the picture look natural, and at the same time some patience will be required to redo areas which don’t succeed at first. Sometime – and that may mean after quite some time – the result could look like this:

And the complete picture then looks like this:

Final optimization (cloning):

With large scale clone operations like this it is practically unavoidable that parts of the picture get overpainted which don’t really need to be altered. Perfectionists as we all are, we can then use the Copy section function to copy parts of the original image to replace the incorrectly edited parts of the new image, so that these edge zones remain largely intact.
When you are ready, it is a good idea to load both the original image and the edited image into PhotoPerfect and then switch from one to the other. It’s really quite impressive to see how the people simply pop in and out of the picture.

Final optimization (other operations):

The dark parts of the image have been significantly brightened and somewhat sharpened:

Here is another example of what you can do with PhotoPerfect (the time required for this approximately 2000x2000 pixel image was about 3 hours):






With large scale restoration work like this it is important to make sure that the results do not look too regular. Therefore some trivial but plausible errors have been introduced, which helps to make the repeated use of a single clone source less obvious.

Cloning certainly takes some practice. You can only work quickly when you don’t need to think twice about when to press CTRL to obtain a new reference point. But to work efficiently as well you need to be able to quickly extend existing structures in a realistic way.

I get a lot of opportunities to exercise my skills when retouching scanned images in order to remove scratches and other irregularities. My scanner cannot do this even using infra-red scanning. Cloning lots of small dots away gives you excellent practice using the CTRL key. You can’t do much wrong and it is mainly a question of perseverance – unless you have a really big patch to repair. Scratches, on the other hand, demand much more effort to create a plausible background.