This image has 3 different regions that are significantly different, namely the sky, the white rocks, and the reddish region in the middle.  If you perform a global histogram adjustment on this image, the image will be enhanced only a minimal amount.  This following steps will carefully select each of the 3 regions, and then enhance each of these regions independently.  We will use the Magic Wand Tool for selecting the sky, the Magnetic Lasso Tool for selecting the white rocks, and then join those two together and use the Inverse to select the red central region.  This example is also done in the Layers Page.

Before talking about how to make a selection, we discuss a few basic things that are crucial in the process.

• The primary selection tools are Lasso, Magnetic Wand, Marquee, and Magnetic Lasso.
• To add to an existing selection, hold the Shift key while making the added selection using any of the tools.
• To subtract from an existing selection, hold the Alt key while making a selection using any of the tools.  This newly selected area will be deleted from the original selection.
• Always Feather your selections right before you apply any image adjustment.  This is done via  Select > Feather  and then input a number.
• To keep the selection active, yet not see the selection boundary (the "marching ants"), you can toggle viewing the boundary with Control-H.
• After applying an adjustment to a selected area, you may want to Deselect the selection via  Select > Deselect.
• Save all selections that you may want to use at some other time (see the example below).
• Zoom in and inspect your selection carefully before you make any adjustments.
• Inverting a selection is extremely useful, as noted in the example below.

Fig. 1.  Before

Fig. 2.  After all of the changes below

Select the Sky

• Click on the Magic Wand Tool (2nd column and 2nd from the top).  This usually works well for selecting areas where the color does not vary much and where there is a clear boundary.  In general, this is a good choice for selecting skies.
• Click most anywhere in the sky
• If selection is not complete, hold the Shit key down and keep clicking.
• If this is not picking up enough, increase the Tolerance for the Magic Wand to a larger number, perhaps in the 20 to 30 range, then keep trying.  Larger Tolerances could cause problems in that other stuff is selected.
• If there are still some left-overs, switch to the Lasso tool and continue adding/deleting stuff to/from the selection.
• Zoom in to check that the selection is accurate.
• Save this selection by Select > Save Selection, then give it a name, such as "Sky."  (We will load this selection later on.)

Enhance the Sky

• Select > Feather  and then input a number.  I used 3 on this 2MP image and this is the number of pixels that acts as a transition to the boundary. I did not want a large transition on the sky.  Without feathering, there could be a noticeable edge artifact, like a tan line.
• Enhance > Adjust Brightness/Contrast > Levels ... (not the Brightness/Contrast).  While in this dialog box, you adjust the histogram range to enhance the image by sliding controls affecting the highlights, midtones and shadows. (See Figure 3 below)
• Move the rightmost triangle under the histogram to the left to adjust the highlights to about 227.
• Do NOT move the left slider triangle to adjust the dark area because we do not want any dark areas in the sky.
• Move the middle slider triangle to adjust the midtones.  I moved it to the right to about .58.
• Click OK.  The resulting adjustment is shown in Figure 4 (which also shows the Magnetic Wand selection discussed next).
• If you do not like the results, click on the "Step Back (edit undo)" button.  In fact, you generally want to bounce back and forth with Step Back and Step Forward to compare the change with what you had before.  In addition, you should zoom in and compare the changes.

Fig. 3  Histogram of the original Sky

Fig. 4  After Sky adjustment and the Magnetic Lasso selection of the White Rocks.

You can now Select > Deselect so that the Sky region is no longer selected.  However, when we start making the next selection, this deselecting will automatically take place.

Select the white rocky region in the lower left using the Magnetic Lasso Tool.  The Magnetic Lasso tool is useful when there is a clear boundary for most of the selection, but the selected area may have a large variation in color.

• Click on the Magnetic Lasso Tool.  To do that, you may need to click on the small black triangle in the lower right of the Lasso Tool, and then select the Magnetic Lasso Tool.
• Click once as close to the edge of the white area as possible.
• Move the mouse slowly along the boundary, and you will observe the magnetic nature of this tool.  Do not worry if some parts of the selection are not great at this stage.
• If you do a single click on the boundary, that point will be a fixed point of the selection.  I f you do that, just keep on moving the mouse slowly along the boundary of the selection.
• When you have finished tracing the boundary of the selection, double click and the selection will be automatically closed by connecting to the initial point.
• It is very likely that there will be some parts of the selection that are not good.  Often you will need to add or subtract from the selection, and it will probably be better to use the Lasso Tool for these modifications.
• See Figure 4 to see the selected region.
• Save this selection by Select > Save Selection, then give it a name, such as "White Rocks."  (We will load this selection later on.)

• Select > Feather  and then input a number.  I used 10 on this 2MP image and this is the number of pixels that acts as a transition to the boundary.  Without feathering, there could be a noticeable edge artifact, like a tan line.
• Enhance > Adjust Brightness/Contrast > Levels ... (not the Brightness/Contrast).  While in this dialog box, you adjust the histogram range to enhance the image by sliding controls affecting the highlights, midtones and shadows. (See Figure 5 below)
• Leave rightmost triangle under the histogram alone because it is bright enough already.
• Move the left slider triangle a little to the right to adjust the dark area.  I moved it to 34.
• Move the middle slider triangle to adjust the midtones.
• Click OK.  The resulting adjustment is shown in Figure 6 (which also shows the selection discussed next).
• If you do not like the results, click on the "Step Back (edit undo)" button.  In fact, you generally want to bounce back and forth with Step Back and Step Forward to compare the change with what you had before.  In addition, you should zoom in and compare the changes.

Fig. 5  Histogram of the original White Rocks

Fig. 6  After White Rocks adjustment and the selection of the Red central region.

Select the Red central region shown in Figure 6

• Select > Deselect to close all previous selections and their feather properties.
• Select > Load Selection and then select the Sky option from the drop down menu. Click OK.
• Select > Load Selection, VIP check the option "Add to selection," and then select White Rocks from the drop down menu.  Click OK.
• At this point, you have selected both the Sky AND the White Rocks.
• Select > Inverse.  This inverts the selection so that everything except what is inside the previous selection is now selected.  The "inverse" is the "complement" of the previously selected set is the Red central region.  This is shown in Figure 6.
• Save this selection by Select > Save Selection, then give it a name, such as "Red Central."

• Select > Feather  and then input a number.  I used 10 on this 2MP image and this is the number of pixels that acts as a transition to the boundary.  Without feathering, there could be a noticeable edge artifact, like a tan line.
• Enhance > Adjust Brightness/Contrast > Levels ... (not the Brightness/Contrast).  While in this dialog box, you adjust the histogram range to enhance the image by sliding controls affecting the highlights, midtones and shadows. (See Figure 7 below)
• VIP!!  In the Channel box near the top, choose "Red" from the drop down menu.
• Move the rightmost triangle under the histogram to the left to adjust the highlights to about 217.
• I did not Move the left slider triangle to adjust the dark area.
• I did not Move the middle slider triangle to adjust the midtones.
• Click OK.  The resulting adjustment is shown in Figure 2 at the top of the page.  I also sharpened the image using the Unsharp filter.
• If you do not like the results, click on the "Step Back (edit undo)" button.  In fact, you generally want to bounce back and forth with Step Back and Step Forward to compare the change with what you had before.  In addition, you should zoom in and compare the changes.
• Adding a little Contrast would be good for this section, but not for the sky or the white rocks (see Contrast Page).  To add contrast,  Enhance > Adjust Brightness/Contrast > Brightness/Contrast.  Move the Contrast slider to the right to about +15.

Fig. 7  Histogram of the Red Channel of the original Red Central region.

Figure 8 shows the original Histogram levels for Figure 1 before any enhancement was performed.  Figure 9 shows the Histogram levels for Figure 2 after all of the preceding steps were performed.
 
 

Fig. 8  Histogram of the original image shown in Figure 1

Fig. 9  Histogram of the final image shown in Figure 2