Capture One Tutorial.
Straighten perspectives.

The laws of perspective mean that a building photographed from the ground appears to narrow towards the top. This is perfectly natural and is how we see the building with our eyes, our brain correcting for it to give us the impression of vertical lines. But when we look at a photograph, our brain doesn't correct it: the verticals appear to be tilted and converging upwards. In architectural photography, you might want the verticals to be parallel to each other.

The first thing to do, of course, is to choose a point of view that minimises the effect of perspective: far enough away from the building (even if it means using a longer focal length) and high up if possible. However, it is not often possible to completely eliminate this distortion, because of a lack of distance, for example. The verticals can then be straightened in post-processing, as we will see in this tutorial.

Note: our tutorial is based on Capture One, but similar work can be done with Lightroom or other raw-processing softwares.

1

Click on the Composition tool tab. If this tab is not available, you can request that it be displayed (see the Capture One customisation tutorial).

Some examples.

Notre Dame church in Saint-Chamond (France).
Despite being set back a long way, the effect of the vertical perspective is noticeable.

The verticals have been straightened.
However, there is still a slight rounding due to the short focal length used when shooting.

Temple of Augustus and Livia,
in Vienne (France).
The lack of hindsight is extremely constraining: the temple is located in a small square surrounded by buildings.

The same building after correction.
The improvement is noticeable. Despite everything, the initial framing was too tight: difficult now to obtain an airy composition.

This bell tower (Marlhes, in France) is necessarily located high up.

After a slight correction by following the method exposed in this tutorial, the rendering is more pleasant.

The back of the Saint-Saturnin church, in Marlhes (France).

There too, the too tight initial framing (in width in any case) complicates the work.

Also to know...

• Another setting can give even more spectacular results for this kind of work. This is the Keystone setting (on this same keystone tool), which allows you to straighten verticals and horizontals in a single operation.
• The straightening of the verticals may require severe cropping to restore the original proportions of the image: do not hesitate to frame wide at the time of the shot, otherwise the bottom or the top of the building risks being cut off, which would still be a shame.
• It is often more natural not to totally cancel the perspective effect: you can simply reduce it.
• Verticals can be straightened as soon as the shot is taken, provided you have a decentring lens or a view camera. However, the use of these tools can be tricky.