8.10. The Adjust Panel
For thousands of people, the handful of basic image- fixer tools described on the previous pages offered plenty of power. But many others wound up disappointed with previous iPhoto versions.
Power users were irked at having to trot off to some other program like Photoshop to make more advanced changes to their pictures, like fiddling with the saturation (the intensity of colors) or the sharpness of the image. Meanwhile, Apple clearly detected that the landscape of inexpensive photo editors was changing; even the most basic free digital shoebox program for Windows offered full-blown image controls.
All of which sets the stage for one of iPhoto 5's most important new features: the Adjust panel (Figure 8-6). It appears whenever you click the Adjust button in editing mode.
Note: Except for the Brightness and Contrast controls, the Adjust palette doesn't work unless your Mac has at least a G4 processor. And if you want to apply these effects to photos in the RAW format, you'll need Mac OS X 10.3.6 or later.
Now, before you launch yourself into the following pages and turn yourself into a tweak geek, here are some preliminary words of advice concerning the Adjust panel:
8.11. Introduction to the Histogram
Learning to use the Adjust panel effectively involves learning about its histogram , the colorful little graph at the bottom of the panel.
The histogram is the heart of the Adjust palette. It's a self-updating visual representation of the dark and light tones that make up your photograph. If you've never encountered a histogram before, this all may sound a little complicated. But the Adjust palette's histogram is a terrific tool, and it'll make more sense the more you work with it.
Within each of the superimposed graphs (red, blue, green), the scheme is the same: The amount of the photo's darker shades appears toward the left side of the graph; the lighter tones are graphed on the right side.
Therefore, in a very dark photographa coal mine at midnight, sayyou'll see big mountain peaks at the left side of the graph, trailing off to nothing toward the right. A shot of a brilliantly sunny snowscape, on the other hand, will show lots of information on the right, and probably very little on the left.
The best-balanced pictures have some data spread across the entire histogram, with a few mountain-shaped peaks here and there. Those peaks and valleys represent the really dark spots (like the background of a flash photo) and bright spots (a closeup face in that flash picture). Those mountains are fine, as long as you have some visual information in other parts of the histogram, too.
The histogram for a bad photo, on the other handa severely under- or overexposed onehas mountains all bunched at one end or the other. Rescuing those pictures involves spreading the mountains across the entire spectrum, which is what the Adjust palette is all about.
8.11.1. Three Channels
As noted on the previous page, the histogram actually displays three superimposed graphs at once. These layersred, green, and bluerepresent the three "channels" of a color photo.
When you make adjustments to a photo's brightness valuesfor example, when you drag the Exposure slider just above the histogramyou'll see the graphs in all three channels move in unison . Despite changing shape, they essentially stick together. Later, when you make color adjustments using, say, the Temperature slider, you'll see those individual channels move in different directions.