Why the BrightnessContrast Command Creates Guesswork

Why the Brightness/Contrast Command Creates Guesswork

So, how does the Brightness/Contrast command lead you down the dark side of color correction? In the figure, the Brightness and Contrast values read +57 and 35, respectively. But +57 and 35 what? You might presume percentages, or something equally relative, and you would be half right. The Contrast value scoots colors toward or away from gray as percentages of their current distance. So a value of100 makes all colors gray, and a value of +100 creates a threshold effect, turning all pixels in each channel either black or white. But Brightness is actually an absolute measurement that adds or deletes a constant amount of brightness to each and every pixel. A typical 24-bit photograph contains as many as 256 brightness levels per color channel (a topic that is discussed at length later in this chapter), so a value of +57 shifts fully 3.5 million of the possible 16 million colors in an image to white. By shielding you from the complexities inherent in color correction, the Brightness/Contrast command gives you no way to adjust some colors more than others, and prohibits you from distributing highlights and shadows with any degree of confidence or uniformity .