Wednesday, January 24, 2007
Understanding and using layers increases your tools and capabilities for refined image processing
Add a Levels Adjustment Layer (in Photoshop, this is in Layers > New Adjustment Layer; click OK or you can click on the Adjustment Layer icon at the bottom of the Layers palette). You'll get the familiar Levels dialog box, but you'll also find that a layer appears over your photo in the Layers palette (new layers always appear over the active layer). Adjust the image as appropriate, then click OK. At this point, no pixel has been harmed in the original image.
Add More Layers
Now you might add a Hue/Saturation Layer to tweak the color of your image. This works the same way-add the layer and you get a familiar dialog box along with a new layer in the Layers palette. You can add saturation, correct the hue of important colors and so forth, then click OK. You now have two layers affecting the appearance of the original photo, but still, original pixels haven't been changed.
Readjust As Needed
As you work an image to make it look its best, sometimes an early adjustment won't look as good later. Perhaps after adding a Hue/Saturation Layer, the photo looks a little dark. No problem. Double-click on the adjustment icon of your Levels Adjustment Layer (the box with the graph-like icon) and your original adjustments reappear. Make any new adjustments as needed and click OK again.
Save your file in the native file format for your program (.psd for Photoshop), and you'll retain all your layers, ready to go to work for you again at any time, even if you shut down the computer in between. This is a major quality advantage. Whenever you adjust an image directly to the original pixels and have to make changes, you're making adjustments on top of adjustments, which can only reduce quality. With Adjustment Layers, that never happens.
Working The Layer Mask
Click on the white box to be sure you're in the Layer Mask. Now use your paintbrush to turn the effects of the Adjustment Layer on or off, using white and black in your toolbar colors. A common expression is "white reveals, black conceals," referring to the fact that white in the Layer Mask turns on the effect of the Adjustment Layer, while black turns it off. Or think of a room at night: turning on the light, adding white light, allows you to see what's in the room; turning off the light makes the room black, preventing you from seeing what's in the room. You then can use a flashlight to find and highlight parts of the room without showing it all.
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