Local corrections use the same Levels layers as Global exposure/color corrections except selections & masks team up to apply changes to restricted areas.
A selection restricts the adjustments you apply to the image, or to a layer, to only the pixels that have been selected. Selection normally applies only to the currently-selected layer, but that can be modified in the Select menu.
Each selection tool bar has buttons to enable creating a new selection, adding to the current selection, or subtracting from the current selection.
Selection tools:
- Marquees
- Used to make geometric selections.
- Pick a marquee tool and experiment with it.
- Click on the Add to Selection button in the tool bar.
- Pick the other marquee tool and add to your selection.
- Experiment with other selection buttons in the tool bar.
- Lassos
- Used to make free form and complex polygonal selections.
- All lassos will close the selection loop to form a selected, or deselected, area.
- Select the Magnetic lasso.
- Magnetic lasso uses edge contrast to set the selection edge semi-automatically, but will not work where there is insufficient contrast.
- Polygonal lasso creates free form geometric selections
- Regular lasso creates freehand selections.
- Magic Wand
- Selects all (contiguous, or not) pixels similar to the one you click on. It works well on very similar areas, but can easily overselect. You have to keep an eye on the whole image.
- Select the Magic Wand. Try it on an image using a variety of Tolerance settings with Contiguous both on and off.
- Modifying selections
- Feathering softens the selection edge to make a smooth transition.
- Select a contrasting area using whatever combination of tools you find appropriate.
- Use Select->Modify->Expand to expand the selection by 100 pixels.
- Use Select->Refine Edge to bring up its dialog box. Left click Custom Overlay Color. Use Cntl-space bar to zoom way in on an edge section.
- Use the Feather and Contract/Expand sliders to adjust the transition. Notice that the transition extends in both directions from the original selection edge. Find a point that does not leave much of a dark edge on the outside of the selection, or much of a colored edge on the inside.
- Saving/loading selections
- Use Select->Save Selection to embed the selection in the image file for possible future use.
- Use Select->Load Selection to load a previously-saved selection, and if necessary replace current selections or combine it with current selections.
Finally the levels layer exposure/color correction is applied with your selection in place, automatically creating a mask.
With a selection in place, and its edge feathered appropriately, use Layer->New adjustment->Levels or Layer Palette->Create Adjustment Layer->Levels
to create the adjustment needed for this particular selection of the image. Be sure to experiment with the preview until you are satisfied. Remember, because it is a layer, you can always turn it off, change its opacity, or just delete it.
