Architectural Photography, Part 4: Fixing Wide Angle Distortion

At the end of the last article, we had corrected the converging verticals and the slight horizontal yaw of our photo, and yet things still aren’t quite right:

The spires appear too thin. The perspective correction has left some unnatural looking shapes, easily observed by comparing the original uncorrected image (left) with the corrected version (right):

While we now have properly rectified verticals, they have come at a price.

Avoiding Wide Angle Distortion

Wide angle lenses can distort objects that appear towards the edges of the frame. The problem often occurs in vertical format images, where the tops of tall buildings appear stretched out, or spherical light fittings in ceilings appear as ellipses.

This happens with both normal and tilt/shift lenses. It’s a natural consequence of linear perspective - it’s a geometric inevitability, not a fault in the lens or camera.

You can avoid this in a few ways:

• Use a longer focal length lens: the longer the focal length, the less the wide angle distortion
• Move back from your subject as needed: this may go hand in hand with the preceding point, but even if you kept the same lens, the subject would be farther from the edges of the frame where distortion is at its greatest

However, in many situations, it’s unavoidable, such as in the case of the east elevation of Durham Cathedral. There’s no way to move further back.

Correcting Wide Angle Distortion

There a number of ways to do this. The simplest is to distort areas of the image using tools such as Photoshop’s Transform/Distort - you can make a selection of the required area and simply deform it to correct the distortion by eye.

However, DxO’s ViewPoint 5 software is dedicated to geometrical and perspective corrections and that’s what we’ll use to try to improve our spires. In fact, if you visit the website, you may note that a number of the example images are buildings with towers, spires, domes or cupolas!

I’m using ViewPoint 5 as a plug-in to Lightroom Classic. I’m using the image at the top of this page as the starting point. As a reminder, this was taken using a Nikkor 14-30mm zoom at 19mm, with the camera pitched upward to fit the building within the frame. The verticals have been rectified using the tools included in Lightroom. I could equally have well used Viewpoint to accomplish this.

With the image opened in ViewPoint, I’m going to start by using the Reshape Fusion tool. This displays a grid of points over the image. You can choose the number of grid points, but for our purposes, the more the merrier, so 32 it is:

The tool has three modes. We’re going to use Move mode so we can pull the pixels around by selecting and adjusting some of the grid points.

Widening the Towers

The towers look overly skinny with the rectified verticals. Let’s widen them out a little. The key to these adjustments is not to overdo things so that they look like obvious corrections that have been applied. Our goal is to achieve a natural look such that the eye is not drawn to features because they look slightly bizarre.

First, we’ll widen the left hand tower. Here, I’ve selected the first few columns of grid points using the mouse:

New in ViewPoint 5 is the Propagation slider. By default, this is at zero, so moving the selected grid points affects only that area of the image and nothing more. However, it’s often useful to enable some amount of propagation for better control and more subtle effects:

The points in red are fully affected by the move. Those in green are unaffected. The orange and yellow colour indicates how the propagation of the move changes. Increasing the propagation further would change more of the green points to yellow or orange as you move right across the image.

Why only select the points to the left of the building? That way we can use propagation to widen just the tower in a highly controlled fashion and avoid making any change at all to the proportions of the main façade.

Next, we click just one of the selected points and we can use the mouse, or even better, the keyboard cursor keys to move the affected part of the image. Here I’ve moved things left.

“ Move ” is slightly misleading, as really this is a similar effect to Photoshop’s Transform/Distort, but with variable distortion depending on the propagation.

Next, we can change the selection and do the same thing on the right hand side:

Let’s look at what we’ve achieved. Here’s a comparison of the left hand spire. The adjusted version with the widened tower and spire is shown on the left:

Hopefully, it’s clear the proportions now appear rather more natural. We’ll the overall effect on the full image below.

Adjusting Local Distortions

There’s more we can do. We still haven’t fully addressed those uncomfortable looking areas on the right side of the left spire. The angles look overly sharp to the eye. We can make a further local adjustment to try to address that. Here, we need very little propagation at all:

With the local selection made and propagation reduced to avoid pulling the roofline out of shape, we’re ready to go. Using the up arrow cursor key, we can move the area up slightly to open up the angles better. Here’s the before (left) and after (right) - it’s a subtle change, but it makes it look much more natural:

We can do the same for the right hand spire too. It takes a little trial and error to get things just right. Remember that you can always change your grid point selection and keep refining things until you achieve the results you want.

And here’s the before (left) and after (right) for the right hand spire:

Final Comparison

Let’s look at the corrected image. On the left is the starting point for this article (vertical and horizontals corrected). On the right is the version with the wide angle distortion corrections:

I haven’t tried to remove all the distortion as it risks introducing new oddities into the image. There’s some compromise between having fully rectified verticals and having no wide angle distortion. Nonetheless, with the wide angle corrections made in ViewPoint 5, I think the final result looks more natural and the spires no longer catch the eye for all the wrong the reasons.

You might decide not to fully rectify the verticals in order to avoid the distortion, but you should know your audience first - some viewers will be much more bothered by converging verticals than any remaining wide angle distortion!

In the next part of this series, we’ll discuss natural light planning for architectural photography.