It’s not one of my best photos but it’s perfect for illustrating this particular issue. It was shot with a Laowa 9mm APS-C ultra-wide lens (around 13.5mm equivalent in full frame terms), and excellent as this lens is, it suffers from the same issue as ultra-wide lenses everywhere.
It’s called ‘volume distortion’ (or volumetric distortion) and it’s where objects near the edge of the frame become wildly elongated. You may have noticed this effect and dismissed it as an inevitable result of the wide angle of view.
That’s fine – until you have people in the frame, and then it becomes a problem, especially if they suddenly appear twice as wide or, if they’re closer to the camera, have ridiculously elongated facial features.
I chose this picture because it has people both at the edges of the frame and in the center, which is perfect for showing that volume distortion is not a straightforward fix.
Notice the man at the left edge of the frame. He appears a lot wider than he was in real life (and probably wouldn’t be terribly flattered). You might think changing the aspect ratio would fix this, but then there are two people in the center of the frame that would become artificially elongated if we simply made the picture taller.
This is a much more complex optical issue, then. It’s also nothing to do with lens profiles, barrel distortion or perspective correction. This is a shift in the way volumes are rendered near the edges of the frame with ultra-wide lenses, and is not tackled at all by mainstream lens corrections.
But DxO has the answer. This is a company that specializes in optical corrections, and it has a handle on this one. Amongst the options in DxO ViewPoint 3 (a separate app) and Perspective Efex (part of the Nik Collection) is an adjustment for Volume Distortion.
I don’t know of any other software that has this (I’m sure someone will tell me if I am wrong) and its effect is both important and profound.
So let’s have a look at this image in Perspective Efex. This plug-in prefers to work from an original image with EXIF data, but it doesn’t insist on it – you simply have to make adjustments by eye instead of applying them automatically.
There are two types of volume distortion correction (volume deformation correction) you can apply. The Horizontal & Vertical option will preserve straight lines but may require more adjustment work, while the Diagonal option appears more immediately effective but leaves straight lines near the frame edges strongly bowed.
I went for the Horizontal & Vertical option here because the shot had architectural detail that needed to stay straight (vertical keystoning is fine, but not strong barrel distortion). And a few moments’ worth produced a dramatically better result.
So in the corrected image, see how the man at the edge of the frame now looks normally proportioned (my word, that shows the original was BAD), but the people in the center have not been distorted – in fact, they look a little more natural too.
I’ve always accepted that this volume distortion at the frame edges was a natural consequence of ultra-wide lenses, but now I see that it’s not – and I’m doubly impressed by Perspective Efex for being able to fix this and make ultra-wide images actually look natural!
- Perspective correction explained
- Lens aberrations and what you can do about them
- DxO ViewPoint 3 review
- Perspective Efex review
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