Tham khảo tài liệu 'professional information technology-programming book part 49', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | . Extending Dynamic Range We ve already covered some techniques for extending dynamic range HDR in Chapter 8 however here s the skinny on three different ways to do it. You ll find all of them useful for different reasons. HDR images are or can be a bit outside of the normal workflow. They are often used as the background layer of an image in which you are going to make further adjustments. . The Basic Manual Method You can make your own EDR image from any two or more flattened images. Ideally these will have a couple of different f-stops of exposure difference. Figure 11-8 shows an EDR image composed by exporting two different exposures from Camera Raw then combining them manually in Photoshop. Figure 11-8. Two different exposures of the same Camera Raw file were used to get the beautifully balanced image on the right. There is immense detail in both extreme highlights and shadows. Also there s much less noise in the shadows and color shift than when using the Shadows Highlights command on this same image. Camera Raw images have such a huge dynamic range that the human eye can t see it all. I So I use the Camera Raw adjustments to create that part of the dynamic range that is visible to make the picture look as much as possible like what I want it to look. But sometimesparticularly in highly textured landscapes with big skiesI want to simulate a much wider range so that I can see detail in just about everything. One of the big advantages of using two Camera Raw interpretations is that there s no need to worry about moving subjects and you don t need a tripod. That s because the content of both images is exactly the same in every respect except brightness range interpretation. The technique I use is to create two interpretations of the same image. I can easily create exposures that are as much as two stops apart if I m working with a 12-bit image often more. Even a 10-bit image will give me the equivalent of two exposures that were made steps apart. .
