Keystoning and Lens Distortion

One of the most common mistakes I see in both real estate photography and architectural photography is what is commonly know as keystoning. This is the perspective issue that causes vertical surfaces (walls) to look like they are leaning. The is usually caused when the camera sensor (or film plane) is not on the same angle as the subject. By keeping your camera perfectly level is one way to avoid this. There are times when you can not have your camera perfectly level, maybe when a house is on a light hill and you are downhill from it. You do not have a choice but to look up at the house. In this situation, there are two options to deal with the situation. The first way is with what is called a perspective control lens, or tilt-shift lens. This gives you the ability to change the angle of the lens, without moving the camera body, to correct for the keystoning. Though this is the best way to correct for the problem, perspective control lenses are very expensive and do not come in ultra wide angles. The second way, and most common is in the post processing. In programs like Adobe Lightroom and Photoshop, you can change the angles to fix any keystoning. Below is an example of keystoning along with what the images should look like with all angles correct. 

Red Lines Show Incorrect Angles

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