Extract is considerably different than the other approaches used in this series of articles. First, it only works on eight bit images. This immediately puts a limitation on the use of this method. Many photographers work primarily on sixteen bit files due to the higher quality that is achieved when compared to eight bit images. Second, the Extract Filter does not produce either a selection or a mask. Rather, it deletes any undesired pixels. The result is an image layer that is transparent where the pixels have been deleted.
In order to extract the statue from the image, it will be necessary to draw an outline along the edges of the statue and then fill the area inside the outline. But first, the settings in the dialogue box must be properly adjusted. While there are a number of settings in the dialogue box, two are of most importance for this image: the Brush Size and Smart Highlighting. The Brush Size sets the size of the brush that is used to paint an outline around the statue. However, when the Smart Highlighting box is checked, the brush size is automatically adjusted to the optimal size for the edge being outlined. The rest of the settings are used as shown in the figure. As this image is worked, it will be necessary to alter the brush size and switch the Smart Highlighting on-and-off as the outline is created in order to create the best outline (i.e., some areas of the statue's edge are best outlined with a narrower brush, some with a wider brush, and some with Smart Highlighting).
To begin the outlining of the statue, the Edge Highlighter Tool is chosen (all of the Extract tools are in the upper left hand corner of the dialogue box) and is used to draw an outline around the statue. To make things easier, the Zoom tool can be used to enlarge the image. The Eraser tool can be used to erase parts of the outline if so desired. Figure 5 shows the dialogue box with the outline.
Sometimes, rather than create the exact selection that is required, it is easier to create another selection and modify it so that it becomes the selection that is needed. There are a number of tools for this purpose.
Selecting the area that isn't desired and inverting the selection is often the easiest way to create a selection. Figure 9 shows an image that was used earlier in Part II of this series. This time, it is necessary to work on the land without affecting the sky. Unfortunately, selecting the land directly would be difficult as the land is a combination of tones and colors. However, it is fairly easy to select the sky. Figure 10 shows a sky selection created with the Magic Wand.
At times, it is very helpful to be able to create a border around an edge. Figure 12 shows an image with a mountain ridge back lit by the sky. The problem with this image is that the edge where the mountain ridge meets the sky is very high contrast. This will likely result in an oversharpened ridge. It is necessary to create a selection that borders this ridge. This selection can then be turned into a mask that is applied to the sharpening layer in order to remove the sharpening along the edge.
Often, a selection is needed that is larger than can easily be selected. In this case, a smaller selection can be selected and expanded to create the desired selection. Figure 17 shows just such a case. This is an image of a valley with an old mining ruin (along the lower edge of the image). The clouds and sky are too bright and need to be toned down. A selection is needed that can be applied to a Curves layer that will darken the sky. However, there is a problem. If just the sky is selected and used to create a mask for a Curves layer, the use of Curves to darken the sky will be obvious and will look amateurish. A better solution is to have the selection overlap the mountains. The selection can then be blurred to create a gradual transition from the selected to the non-selected areas.
Once a Gaussian Blur has been applied to the selection, the selection can be used to create a mask for the Curves layer.
The nice thing about the expanded selection is that it follows the contour of the mountain ridge (i.e., the edge of the expanded selection is always a given distance, in pixels, from the ridge). Thus, the blurring can be adjusted so that the blurring stops just at the ridge -- along the entire selection.
Sometimes, a selection is needed that is smaller than can easily be selected. In this case, a larger selection can be selected and contracted to create the desired selection. Figure 21 demonstrates this situation. This old pioneer cabin needs a little extra sharpening. However, the edges of the cabin are high contrast with the surrounding area and sky. The extra sharpening could easily over sharpen these edges. Thus, it is necessary to sharpen the boards of the cabin without sharpening the edges of the cabin.
For complicated selections, it is often impossible to get a high quality selection with just one tool. For example, part of the desired selection may be best handled with the Color Range tool, another part with Calculations, and another part with the Magnetic Lasso. In cases like this, the selection is best created by using multiple tools. There are two approaches to this. Sometimes, the first selection can be directly modified by additional tools. For instance, the Magic Wand can be used to add or subtract from a selection. In other cases, each tool will be used to create a separate selection which is then saved (choose Select/Save Selection). Figure 26 shows the Save Selection dialogue box.
After all of the selections have been made, they can be opened one at a time (choose Selection/Load Selection) and combined in a manner that will create the desired, final selection. Figure 27 shows the Load Selection dialogue box. The bottom of the dialogue box has four options for opening a selection. These options determine how the selection being opened will combine with any selection that is already open:
Using these options should allow a final selection to be created from the saved selections.
Each of the tools presented in this series works best for a particular type of selection. With practice, any photographer can learn to identify the best tool, or combination of tools, for a needed selection.