Digital Darkroom

Tools like Clone Stamp and Spot Healing Brush have an extra setting in the Options bar called Sample All Layers. With this setting selected, the tools will use the contents of all layers for the stamping or healing action but will only apply these changes to the current active layer. Storing your retouching changes on a separate layer means that you can always revert back to the original unretouched photo if needed.

1) Start by opening a photo. Next, create a new layer directly above the background or image layer. You can do this by clicking the New Layer button at the bottom of the Layers palette. Rename the layer "Retouching."

2) Next, make sure that this layer is active and then choose the Spot Healing Brush or the Clone Stamp tool. Select the Sample All Layers option in the tool's option bar. This action switches the tool from a mode where the samples are sourced and applied to the same layer. Now all layers in the document become the source of the sample and the changes are applied to the retouching layer only.

3) Now you can start the retouching process. Employ the retouching tools as you would normally but ensure that the Retouching layer remains active when switching between Clone Stamp and Spot Healing Brush options.

4) If after retouching you want to make any global changes to the color, brightness, or contrast of the photo then perform these alterations with an adjustment layer situated above both the image and retouching layers. This way the enhancements will be applied to both layers equally.

Adjustment Layers
These special editing layers alter the look of other layers that are arranged below them in the stack. They act as a filter through which the lower layers are viewed. You can use adjustment layers to perform many of the enhancement tasks that you would normally apply directly to an image layer without changing the image itself. Photoshop CS2 contains 12 different adjustment layers which are grouped with the fill layers under the Create Adjustment Layer button of the Layers palette. Using adjustment layers to make changes to your photos is a great way to edit nondestructively.

Adjustment layers available in Photoshop CS2:
Levels--Adjusts the tones in the picture.
Curves--Adjusts the tones in the picture.
Color Balance--Used for adding or removing color casts from images.
Brightness/Contrast--Lightens, darkens, and controls contrast.
Hue/Saturation--Changes the color and strength of color in photos.
Selective Color--Adjusts the hue of a single group of colors.
Channel Mixer--Changes the color makeup of individual channels and in the Monochrome mode creates great black and white conversions from color pictures.
Gradient Map--Changes the photo so that all the tones are mapped to the values of a selected gradient.
Photo Filter--Reproduces the color changes of traditional photo filters.
Invert--Reverses all the tones in a picture, producing a negative effect.
Threshold--Converts the picture to pure black and white with no grays present at all.
Posterize--Reduces the total number of colors in a picture and creates a flat paint (or poster)-like effect.

The Layers Palette
The Layers palette groups all your layers and their settings in one place. You can display the palette by selecting Window>Layers.

Individual layers are shown, one on top of the other, in a "layer stack." The composite image you see in the work space is viewed from the top down through the layers. Each layer is represented by a thumbnail on the left and a name on the right.

You can edit or enhance only one layer at a time. To select the layer that you want to change you need to click on the layer. At this point the layer will change to a different color from the rest in the stack and is now called the active layer (3).

Layers can be hidden from display in the work space by clicking the eye symbol (4) on the far left of the layer so that it is no longer showing. This action removes the layer from view but not from the stack. You can redisplay the layer by clicking the eye space again.

The Blend mode (1) and Opacity (2) of individual layers can be altered using the controls at the top of the palette. New layers (5) as well as new adjustment or fill layers (6) can be created by clicking the buttons at the bottom of the palette. Also positioned here is the Dustbin button (7) which is used to delete unwanted layers. The Lock Transparency (8) and Lock All (9) buttons are located at the top of the palette just below the Blend mode and Opacity options and are designed to restrict layer changes.