I'm sure you know by now that there are anywhere from three to six different ways to do things in Photoshop, and some methods are faster and more accurate than others. But more importantly, some techniques offer a lot more flexibility, and these methods are the ones you should consider—particularly if you're going to be doing a lot of editing after the fact.
Here's a simple example: You want to lighten a portion of a photograph, so you make a feathered selection and then use the Levels command (Command-L [PC: Control-L]) to lighten the image. Finally, you Deselect (Command-D [PC: Control-D]) and save the document. Although there's nothing "wrong" with this method, it does have a significant drawback: The change is permanent.
In this case, there's really no possibility of changing your mind—you saved the document after lightening the selected area. If you decide that it's too light or you selected the wrong area, it's too late to make an adjustment. Instead, why not use a Levels adjustment layer? (Simply select Levels from the Create New Adjustment Layer icon at the bottom of the Layers palette) to lighten the selected area.) Then, even after saving the document, you can make further adjustments to the Levels and you can use the layer mask to adjust the affected area. This simple change in approach makes a huge difference in the amount of flexibility you can have in your work.
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
- Make a rectangular selection of the area that you want to be in color.
- Choose Select > Transform Selection to angle the selection. From the Select menu, choose Inverse.
- From the Image menu, choose Adjustments > Desaturate. Press Shift-Command-I (PC: Shift-Control-I) to get back to your original selection.
- From the Edit menu, choose Stroke. Enter 12 for the amount and change the Position to Inside.
You 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 is next to impossible to change anything because you worked directly on the Background layer, altering the pixels. (This is often referred to as destructive editing.)