sáng lá. Số lượng nhỏ các tấn ở phía trái tương ứng với sự phân bố thưa thớt của nhạc rất tối, nhất là trong bóng tối. Một hình ảnh quá lâu có thể có hầu hết các tông tập trung tại phía bên phải của biểu đồ, và một hình ảnh thiếu sáng có lẽ sẽ có hầu hết các tấn tập trung ở phía bên trái. Lệnh Levels, thảo luận trước đó trong cuốn sách này, cho phép bạn thực hiện điều chỉnh cho các nhà phân phối. | 214 Adobe Photoshop CS2 Photographers Guide brightest leaves. The small number of tones at the far left correspond to the sparse distribution of very dark tones chiefly in the shadows. An overexposed photo might have most of the tones concentrated at the right side of the histogram and an underexposed photo would probably have most tones concentrated at the left side. The Levels command discussed earlier in this book lets you make adjustments for these lopsided distributions and includes its own histogram display. Photoshop CS had a brand-new Histogram Palette which provides a lot more information to work with. You can see this palette s live histogram display in Figure . Several views are available the illustration shows the expanded view with combined RGB histogram at the top and separate red green and blue channel histograms arrayed at the bottom. In between are some information readouts that I ll explain shortly. You can also select an expanded view that hides the separate RGB histograms and a basic version with no extra data as shown in Figure . If the Histogram Palette is not visible on your screen you can access it by choosing Window Histogram. The numeric display in the middle of the palette probably looks like a lot of mumbo jumbo on first glance but as you become experienced using the Histogram Palette you ll find this information increasingly valuable. Among the data on display are Figure Photoshop CS Histogram Palette shows a live interactive view of the tonal values present in your image. Mean. This represents the average intensity value of all the pixels in the image. If the number is very low that will confirm that the image is rather dark a high number means that the image is on average very bright. Standard Deviation. This is a statistical term that tells you how much the intensity values vary from each other. A low number can mean that the contrast of the image is low while a high number can point to a high contrast image. Median.
