Today’s Question: When doing a panorama of a building, how should I compensate for distortion of the building lines?
Tim’s Quick Answer: There are several approaches here, depending on the specific situation you’re facing. Using a lens with a relatively long focal length and therefore moving a greater distance from the scene can help minimize distortion. Moving parallel to the line of buildings rather than panning from a single position can provide an excellent solution. And a tilt/shift lens may offer an ideal result in certain circumstances.
More Detail: The key with creating a panoramic image of a line of buildings is to minimize the overall distortion in the original captures. If you capture a sequence that translates into severe perspective distortion for the overall composite panorama, it can be very difficult (if not impossible) to resolve that distortion in post-processing. At a minimum, distortion in the initial panorama will require significant cropping.
By using a longer lens focal length and therefore moving a greater distance from the scene in order to capture the frames for the composite panorama, you will also reduce the overall distortion. This approach helps to minimize the reduction in the size of objects out toward the outer reaches of your panorama. That is because this approach reduces the degree of variation in the actual distances between you and the buildings in the scene you are photographing.
Of course, moving a relatively large distance away from a line of buildings isn’t always possible due to the presence of other buildings or obstructions. In that case, changing your position for each capture can help minimize distortion compared to capturing all of the frames from a single position and rotating the camera for each capture.
When taking this approach you will want to use a higher amount of overlap between frames. I recommend overlapping by about 50% rather than the more typical 20% overlap for composite panoramas. It is also important to move in a path that is parallel to the line of buildings you are photographing, so that each capture is created from the same distance away from the “front” of the line of buildings you’re photographing.
This approach of moving the camera position along a path that is parallel to the scene you are photographing can also be helpful when capturing composite panoramas of macro subjects, by the way.
For scenes that are not especially wide, and that you might otherwise be able to capture with no more than about three frames, a tilt/shift lens may provide a perfect solution. After getting the camera setup at the center point of the scene you are photographing, you can then use the shift function of the lens to slide left and right, capturing separate frames for the composite panorama at the far left, center, and far right positions.
Each of these approaches can help you create initial captures for a composite panorama that have minimal distortion to overcome in post-processing. I generally find that the approach of moving the camera for each capture is the most consistently useful option, but the right answer depends on the specific circumstances under which you’re photographing.