The Histogram Palette
The new Histogram palette is a really useful addition to Photoshop and, used properly, can help you make sure that your adjustments don't get out of control and end up harming your images instead of improving them. So, now that you have an idea of how to think about Curves, let's figure out how to use the Histogram palette (Figure 6.70) to make sure we don't go too far with our adjustments. To display the Histogram palette, choose Window > Histogram.
Figure 6.70. The Histogram palette.
A histogram is a simple bar chart that shows you the range of brightness levels that your image is made out of and how prevalent each shade is compared to the others. When you look at the histogram, imagine that there's a gradient stretched across the bottom of the bar chart that has black on the left and white on the right (Figure 6.71). Then if you look above any shade of gray, you can see if that brightness level is present in your image. If there's a bar above the shade, then it's used somewhere in your image. If there's no bar, then that brightness level is nowhere to be found in your image. The height of the bar indicates how prevalent a particular brightness level is compared to the others that make up your image.
Figure 6.71. Imagine that there is a gradient below the histogram.
When you start to adjust an image, the Histogram palette will overlay a histogram that represents the current state of the image (black) with another histogram that represents what the image looked like before you started adjusting it (gray) (Figure 6.72).
Figure 6.72. The gray histogram reflects the unadjusted image, whereas the black version reflects the adjusted image.
