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An in-depth Adobe Photoshop Tutorial explaining how to create an action to whiten teeth. I have gone through the steps fairly quickly in this tutorial but explained and zoomed in to what I was doing. I did this so it is efficient when you are trying to learn, there is not a lot of extra talking. You will probably need to pause the tutorial if you are editing while watching the video.
50 Best Photo Retouching Masterpieces - Photoshop After Before Photos