This movie extract is from Adobe Photoshop CS4 for Photographers: The Ultimate Workshop.
One of the top requests for Camera Raw and Lightroom has been to include perspective corrections, so that users can apply perspective corrections to raw images. It so happens there is already a method in Camera Raw and Photoshop that will allow you to correct the perspective of a raw photograph while keeping the image in its original raw file state. This isn’t exactly a hidden feature in Camera Raw, but this movie does demonstrate a workaround for correcting perspective of raw files while keeping them fully editable in Camera Raw. Here’s how it can be done.
Please note this video is in Quicktime format. A player can be downloaded from apple.com.