Layers

First, here's a detailed example of a method that creates the desired effect but is not very flexible, compared with the flexible way of achieving the same finished product. The result we're going for is to create the look of a color snapshot on top of a black-and- white photo.

Destructive Editing Method

Step One.

Make a rectangular selection of the area that you want to be in color using the Rectangular Marquee tool (M).

DAVE MOSER

Most Flexible Photoshop CS2 Methods

Layers

Duplicating the Background layer

Adjustment layers

Clipping masks

Layer masks

Type layers (as opposed to rasterizing)

Smart Objects

Layer styles

Layer comps

Sample All Layers option

Save as layered PSD (as opposed to flattening)

Step Two.	Choose Select>Transform Selection and click-and-drag outside the bounding box to angle the selection. From the Select menu choose Inverse.
Step Three.	From the Image menu choose Adjust-ments>Desaturate. Then press Shift-Command-I (PC: Shift-Control-I) to get back to your original selection.
Step Four.	From the Edit menu choose Stroke. Enter 12 for the Width amount and change the Position to Inside.

You've created the look of a color snapshot on top of a black-and-white photo. But now you want to do some tweaking. If you take a look at the Layers palette, you'll see that once you've saved and closed, it would be next to impossible to change anything since we worked directly on the Background layer, altering the pixels (this is often referred to as "destructive editing").

Non-Destructive Editing Method

The alternate approach is a non-destructive, extremely flexible method that will often take a couple of extra steps to complete, but will save precious time if you need to make changes later. Here's how it would work in this example:

Step One.	Press the letter M to use the Rectangular Marquee tool to make a rectangular selection of the area that you want to be in color.
Step Two.	Angle the selection by choosing Select> Transform Selection and grab the corners to rotate it.
Step Three.	Click on the Create New Adjustment Layer pop-up menu in the Layers palette and fill the selection with any color other than white by going to Edit>Fill.
Step Four.	From the Layers palette, use the Add a Layer Style pop-up menu to add a Stroke. Enter 12 points for the Width and change the Position to Inside. While still in that dialog, add a Drop Shadow.
Step Five.	In the Layers palette, lower the Fill to 0%. (This will keep the layer effects visible but remove the fill colorthat's why the color was unimportant.) Double-click on this layer in the Layers palette and rename it "frame."
Step Six.	Hold down Command (PC: Control) and click on the layer thumbnail to load the original selection. From the Create New Adjustment Layer pop-up menu choose Hue/Saturation.
Step Seven.	In the Hue/Saturation dialog lower the Saturation to -100 and change the Lightness to around 16 (it will vary with the image). Click OK. Initially the image will be the opposite of what you wantthe snapshot will be black and white and the remainder will be colorbut we'll fix that next.
Step Eight.	Press Command-I (PC: Control-I) to Invert the layer mask and make the effects of the adjurstment layer affect only the areas outside our "snapshot."

Invert the Selection?

You might think that inverting the selection before adding the adjustment layer would work, but it won't. If you invert the selection, the layer mask created for the adjustment layer will stop at the edges of the image, so when you try to move the adjustment layer, you'll see the limits of the mask. That's why this seemingly excessive step is actually necessary.

Hold down Shift and select both the Frame layer and the adjustment layer. Using the Move tool (V), reposition the two layers while preserving the effect. You can even use Free Transform (Command-T [PC: Control-T]) to rotate or scale the original frame to change the effect.

Now, compare this Layers palette with the first method: this time the Background layer is untouched, and the other layers offer as much flexibility as we will ever need. In this example we took advantage of the following methods:

Used layer effects to add the stroke (rather than using Edit>Stroke).
Lowered the Fill percentage to allow only the layer effects to show.
Added an adjustment layer to "temporarily" change the look of the photo.

By using these effects we can:

Decide to abandon the whole idea since the Background was left untouched.
Adjust the angle, location, or size of the snapshot.
Change the size or color of the stroke, and the look of the drop shadow.
Alter the look of the image: for example, giving it a slight amount of color as opposed to completely gray.

The main purpose of that exercise was to demonstrate that using a non-destructive approach sometimes takes a step or two longer, but rewards you with greater flexibility, avoiding potential problems. So, with that last exercise in mind, let's explore all of my nominees for the most flexible Photoshop CS2 tools and techniques.