Perspective Distortion

When we look up at the facade of a building, we are used to seeing the higher parts smaller than the areas below. The camera sees it the same way. We don’t think anything is distorted. That’s just the way light – and perspective views – work.

When we see a photo of a whole building that shows similar narrowing at the top, it appears to us as distorted. Some call it the “falling-over building syndrome”. Such photos are just not very satisfying.

What can you do?

First, understand that perspective “distortion” is not caused by your lens, it comes from the geometry of the situation. Parts of the building closer to you look bigger, to you and your camera. Parts farther away or farther up will look smaller. This happens in proportion to the distances involved. A window, say on an upper floor might be twice as far from you as one that is close and at ground level. That upper window will look half the size. Reduce the distance proportion and the perspective will not be as exaggerated. Back off!

Here is the same hospital photographed from farther away. Still nowhere near perfect, but much better that the other photo. So, back off, and the perspective will be better. Back off more and it gets better still. But there is more that you can do.

Here is the trick to use:

Level your camera so that the sensor plane is parallel to the vertical plane of the building. Yes, that means that the horizon has to go smack through the center of the frame. Not the best for dynamic composition, but cropping can correct that.

Here is a photo with the camera essentially level. Note how the far building looks perfectly acceptable. Why is that? You might ask. If you looked at the geometry, you’d see that inside the camera the distance between the sensor and the “center” of the lens at the top or bottom part of the image is larger than the distance at the center. And so are the distances to the center and top part of the actual situation. They are in fact proportional, and that makes for the “perfect perspective correction”. You can draw out the light rays and the optical paths, but just try it to convince yourself that this is the approach for good building photography.

The photo as it was taken, full frame on the left. A cropped part on the right. If you don’t want to crop and have money to burn, buy a shift lens. To tell the truth, this post was inspired by a question asked over in Ask Ludwig, How does a tilt-shift lens correct perspective distortion?

Yes, you can make corrections in post-pocessing

Just about any photo editor offers a way to adjust perspective. Here is the second hospital photo with such correction applied using the ON1 Photo RAW editor.

I like to leave just a little bit of that distortion when making the corrections in post-processing. I think photos look just a little more natural that way. I did not crop the photo after the perspective adjustment to let you see how the image was squeezed together at the bottom (the editor lets the sides at the top fall out of the frame).

So there you have it. No more “building falling-over syndrome” – three ways to make the photo look real and professional: Back away from your subject, level the camera (horizon in the middle), and use the perspective adjustment tool in your editor.