6. Image Adjustment Fundamentals: Stretching and Squeezing the Bits
Tonal manipulationadjusting the lightness or darkness of your imagesis one of Photoshop's most powerful and far-reaching capabilities, and at first it may seem like magic. But there's nothing magical about it. Once you understand what's happening as you adjust the controlsit all comes back to those ubiquitous zeros and onesit starts to look less like magic and more like clever technology. But your increased understanding and productivity should more than make up for any loss of the sense of wonder, and besides, you'll have more time to play.
Tonal manipulation makes the difference between a flat image that lies lifeless on the page and one that pops, drawing you into it. But the role of tonal correction goes far beyond that. When you correct color in an image, you're really manipulating the tone of the individual color channels.
In fact, just about every edit you make in Photoshop involves tonal manipulation. In Chapter 7, The Digital Darkroom, we'll show you some more esoteric techniques for getting great-looking images, but in this chapter we'll concentrate on the fundamentalsthe basic tonal manipulation tools and their effects on pixels. Much of this chapter is devoted to two toolsLevels and Curvesbecause until you've mastered these, you simply don't know Photoshop! But we also cover the considerable number of other useful commands found on the Adjustments submenu in the Image menu.