Tham khảo tài liệu 'professional information technology-programming book part 36', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | . Lens correction From a strict workflow standpoint lens correction should be done at the same time as other full-screen special effects. Just make sure you duplicate your image file flatten it and copy it to the original image file on its own layer. That way the destructive processes that you re about to do will be on a separate layer. If you have to redo this just throw out the layer that contains your last attempt then duplicate flatten and copy again. There are three facets to lens correction perspective correction pincushion and barrel distortion. You can use Photoshop CS2 s new Lens Distortion filter to correct all threeand more. You can remove any chromatic fringing that you didn t get in Camera Raw or that you haven t been able to clean our of a JPEG image. You can rid yourself of the vignetting that often occurs when you use very wide angle lensesa common practice in architectural photography. You can also crop and resize your image to fit the original space. Figure 8-28 shows an image that has all these problems and the result of fixing it with the Lens Correction filter. Figure 8-28. You have to look closely but in addition to the obvious perspective distortion that resulted from tilting up with a 28mm equivalent lens there is a slight amount of barrel distortion and vignetting in the original image. Here s how the corrections to Figure 8-29 were made 1. After opening the image in Photoshop and making other corrections I duplicated flattened and copied the duplicate image. Then it was pasted into the original image where it became a new layer which is the target layer for this technique. Be sure it remains the selected layer for the remainder of this exercise. 2. I chose Filter Distortion Lens Correction. The result was the dialog you see in Figure 8-29. This dialog lets you combine a number of corrections that before Photoshop CS2 had to be made with separate commands interfaces and even third-party filters. 3. I removed the vignetting that is .
